On the superdollar, and why counterfeiting is hard

“A superdollar (also known as a superbill or supernote) is a very high quality counterfeit United States one hundred-dollar bill,[1] alleged by the U.S. Government to have been made by unknown organizations or governments…. [the] name derives from the fact that the quality of the notes exceeds that of the originals.”

— Wikipedia, “Superdollar

Wikipedia’s dry sense of humor grows on you for sure.

I first read about the superdollar years ago in a Reader’s Digest article of which I now recall nothing save a hazily-remembered description of the 5,000-ton intaglio printing press machines used to make it, which were supposed to be identical to the ones the U.S. federal government’s Department of the Treasury (more precisely, its Bureau of Engraving and Printing). Here’s Wikipedia describing the production of supernotes:

The notes are said to be made with the highest quality of ink printed on a cotton/linen blend, and are designed to recreate the various security features of United States currency, such as the red and blue security fibers, the security thread, and the watermark. Historically notes were often printed using the intaglio printing process, but nowadays offset printing or color inkjet and laser printing is most common.[8]

Experts who have studied supernotes extensively and examined them alongside genuine bills point out that there are many different varieties of supernotes. In 2006 the “family” of fraudulent bills was thought to have 19 members,[9] but since 2006 producers of the supernotes have improved the product, and more varieties exist. Early versions of the fake notes, for example, lacked the bands of magnetic ink printed in distinctive patterns on different denominations of U. S. money; later counterfeits rectify this error.

Several of the inconspicuous “mistakes” on the first supernotes were corrected, some several times. On the genuine $100 bill, for example, the left base vertical line of the lamp post near the figure on the reverse of the $100 note is weak. The first supernotes printed this line too distinctly, rendering the counterfeit more authoritatively printed than the original. Later supernotes over-corrected this strong line by removing it altogether. Similarly, the hands of the clock on Independence Hall on the genuine bill extend slightly beyond the inner circle; on the supernotes they stop short of it. On the front of the supernote, in the “N” in “UNITED STATES,” a slash can be seen to the right of the diagonal and the right ascender of the letter; there is none on the genuine note.

Other differences in vignetting and in the defining lines of the top ornament in Independence Hall have been observed. Klaus Bender and others have speculated that the counterfeiters introduced these differences to be able to distinguish their product from the original, but there is no obvious way to confirm this.

(Intaglio, if you were wondering, “is a family of printmaking techniques in which the image is incised into a surface, known as the matrix or plate, and the incised line or area holds the ink”. It’s used for making bills “because of its ability to produce extremely fine detail that remains legible under repeated handling and is difficult to counterfeit” – see the quoted section below for more info on this in particular. Go here for more on intaglio.)

Interestingly, how actual bills are manufactured is explained in quite awesome detail here; I’ll reproduce the relevant portion below. I didn’t expect to be able to come across this information within about ten seconds of Googling for it in light of counterfeiting worries, but here goes:

In the United States, all paper money is engraved and printed by the Bureau of Engraving and Printing, which is part of the Department of the Treasury of the federal government. The Bureau also prints postage stamps, savings bonds, treasury notes, and many other items. The main production facility is located in Washington, D.C., and there is a smaller facility in Fort Worth, Texas. Every day, the Bureau prints approximately 38 million pieces of paper money. About 45% of this production are $1 bills and 25% are $20 bills. The rest of the production is divided between $5, $10, $50, and $100 bills. Although the $2 bill is still in circulation, it is rarely used, and therefore is rarely printed. Each bill, regardless of its denomination, costs the government about 3.8 cents to produce.

There are 65 separate operations in the production of paper money. Here are the major steps:

Engraving the master die

  • 1 Engravers hand cut the design into a piece of soft steel, known as the master die, using very fine engraving tools and a magnifying glass. The portrait and images consist of numerous lines, dots, and dashes which are cut in various sizes and shapes. The fine crosshatched lines in the background of the portrait are produced by a ruling machine, and the scrollwork in the borders are cut using a geometric lathe.
  • 2 Every time a new Treasurer of the United States or a new Secretary of the Treasury is appointed, their signatures must be engraved on a new master die for each denomination bill. First the signatures are photographically enlarged. An engraver then traces the signatures by hand with one end of a device known as a pantograph. This motion is mechanically reduced through a set of linkages, causing several diamond-tipped needles on the other end of the pantograph to cut the signatures into the master dies.

Making the master printing plate

  • 3 Once the master die has been inspected, it is heated and a thin plastic sheet is pressed into it to form a raised impression of the design. Thirty-two of these raised plastic impressions are bonded together in a configuration of four across and eight down to form what is known as an alto. The master die is then placed in storage.
  • 4 The plastic alto is placed in an electrolytic plating tank and is plated with copper. The plastic is stripped away leaving a thin plate of metal, known as a basso, with 32 recessed impressions of the design. The metal basso is then cleaned, polished, and inspected. If it passes inspection, it is plated with chromium to make the surface hard, and it becomes a master printing plate.

Printing the front and back of the bills

  • 5 The principal printing process is known as intaglio printing. This process is used because of its ability to produce extremely fine detail that remains legible under repeated handling and is difficult to counterfeit. A stack of 10,000 sheets of paper is loaded into a high-speed, rotary intaglio printing press. Each sheet is sized to allow 32 individual bills to be printed on the same sheet. The paper is inspected to ensure that it contains the proper security thread for the denomination to be printed. A master printing plate of the proper denomination is secured around the master plate cylinder in the press.
  • 6 The rotating master printing plate is coated with ink. A wiper removes the ink from the surface of the plate, leaving only the ink that is trapped in the engraved recesses of the design. A sheet of paper is fed into the press where it passes between the master plate cylinder and a hard, smooth impression cylinder under pressures reaching 15,000 psi (1,034 bar). The impression cylinder forces the paper into the fine, engraved lines of the printing plate to pick up the ink, leaving a raised image about 0.0008 in (0.02 mm) above the paper. This process is repeated at a rate of about 10,000 sheets per hour.
  • 7 The printed sheets are then stacked on top of each other. The backs are printed with green ink first and are allowed to dry for 24-48 hours before the fronts are printed with black ink.

Printing the colored Treasury seal and serial numbers

  • 8 After the intaglio printing process, the stacks are cut into two stacks of 10,000 sheets and are visually examined for defects. Each sheet is fed into a letterpress which prints the colored Treasury seal and serial numbers on the face of the bills. Sixteen serial numbers are printed at the same time. The press then automatically advances the numbers before the next sheet of sixteen is printed. The numbers on any sheet are separated by 20,000 between adjacent bills. Thus, the bill in the upper left-hand corner of the first sheet would be serial number 0000001 and the one below it on the same sheet would be 0020001, and so on. On the second sheet, all the numbers would advance by one giving 0000002 in the upper left, 0020002 below it, etc. In this manner, when the sheets are cut into separate stacks, the bills within each stack will have sequential serial numbers.
    Paper Currency
  • 9 The finished sheets are inspected with machine sensors, and any printing errors, folded paper, inclusion of foreign objects, or other defects are identified. Any bills which are found to be defective are marked for later removal. Such bills are replaced with star notes which are numbered in a different sequence and have a star printed after the serial number.

But I digress, so let’s go back to supernotes. Slate:

Government agents say that most funny money falls into three categories.

The first two are relatively easy to spot. Traditional fakes come from a process called offset lithographythat produces phony dollars without the “raised ink” feel of genuine bills. Digital forgeries, made with high-tech scanners and printers, also lack the texture of the real thing.

Supernotes are more deceptive. They’re printed on cotton-fiber paper using the same expensive “intaglio” printing presses used by the U.S. government. An intaglio press creates tiny ridges on a piece of paper by forcing it into the ink-filled grooves of an engraved plate at very high pressure. That’s what gives dollars—and Supernotes—their characteristic feel.

Anyway, the whole point of this post was to call attention to David S. Rose’s excellent Quora answer to the question of why people haven’t been able to figure out “the formula” for printing money; as is my wont (where did that come from anyway?) with high-quality answers I’m reproducing this in full, but the comments section is enlightening to read through too so you’re encouraged to go to the original answer itself for more:

There is no one “formula” for printing money. But because it is so tempting to consider making your own at home, governments have been engaged for centuries in an ever-escalating battle with counterfeiters.

Counterfeiting of money is one of the oldest crimes in history. It was a serious problem during the 19th century when banks issued their own U.S. currency. At the time of the Civil War, it was estimated that one-third of all currency in circulation was counterfeit.  At that time, there were approximately 1,600 state banks designing and printing their own notes. Each note carried a different design, making it difficult to distinguish the 4,000 varieties of counterfeits from the 7,000 varieties of genuine notes.

It was anticipated that the adoption of a national currency in 1863 would solve the counterfeiting problem. However, the national currency was soon counterfeited so extensively it became necessary for the government to take enforcement measures. On July 5, 1865, the United States Secret Service was established to suppress counterfeiting.

Every time the bad guys figure how to print realistic-looking currency, the government changes the way the real stuff is made, to make it ever harder to forge. This began by moving from letterpress-printed, flat currency, to engraved, intaglio-printed currency, which gave the ink a raised appearance that could be felt by hand. Engraving also enabled extremelyfine lines and sharp edges that were difficult for an unskilled criminal to reproduce. They printed the bills in multiple colors (shades of green and dark green), each of which would require a carefully calibrated additional pass through the printing press. And then they went even further, and commissioned special paper to be manufactured in secure factories, of 75% cotton and 25% linen, that had a special feel to it, had red and blue fibersmixed into the pulp, and was commercially unavailable (not to mention illegal to attempt to reproduce.)

As counterfeiters succeeded in carefully engraving plates to duplicate real bills, the Treasury Department began making small variations in the designs of each series, which would make the forgers re-do their whole plate in order to stay current. For example, on the $20 note, the portrait of Andrew Jackson shows him gripping the front of his coat. In the 1934 Series, you can see one of his fingers in the oval frame. But when it was re-designed in 1950 they carefully redrew the portrait to show a second finger!

But over time, the crooks got smarter, and with new technologies, such as color copying machines, a larger number of unskilled people were able to get into the fake money business. This occasioned a lot of federal soul-searching during the 1980s, and by 1990 all US currency incorporated two additional major security features that were very, very difficult to fake:

Security Thread: A security thread is a thin thread or ribbon running through a bank note substrate. All 1990 series and later notes, except the $1 and $2 notes, include this feature. The note’s denomination is printed on the thread. In addition, the threads of the new $5, $10, $20 and $50 notes have graphics in addition to the printed denomination. The denomination number appears in the star field of the flag printed on the thread. The thread in the new notes glows when held under a long-wave ultraviolet light. In the new $5 note it glows blue, in the new $10 note it glows orange, in the new $20 note it glows green, in the new $50 note it glows yellow, and in the new $100 note it glows red. Since it is visible in transmitted light, but not in reflected light, the thread is difficult to copy with a color copier which uses reflected light to generate an image. Using a unique thread position for each denomination guards against certain counterfeit techniques, such as bleaching ink off a lower denomination and using the paper to “reprint” the note at a higher value.

Microprinting: This print appears as a thin line to the naked eye, but the lettering easily can be read using a low-power magnifier. The resolution of most current copiers is not sufficient to copy such fine print. On the newly designed $5 note, microprinting can be found in the side borders and along the lower edge of the portrait’s frame on the face of the note. On the new $10 note, microprinting appears in the numeral “10” in the lower left-hand corner and along the lower edge of the portrait’s frame on the face of the note. On the Series 1996 $20 notes, microprinting appears in the lower left corner numeral and along the lower edge ornamentation of the oval framing the portrait. On the $50 notes, microprinting appears on the side borders and in Ulysses Grant’s collar. On the $100 notes, microprinting appears in the lower left corner numeral and on Benjamin Franklin’s coat. In 1990, 1993 and 1995 series notes, “The United States of America” is printed repeatedly in a line outside the portrait frame.

So the bad guys upped their game as well. They printed simulacrums of the security thread, and counted on the fact that casual users wouldn’t pull out a magnifying glass to read the microprinting. And bogus bills continued to flood the market. Now the fight began to escalate in earnest, with ever-increasing speed.  In the 1996 and later series, half a dozen additional security features were added to American printed currency:

Watermark: The watermark is formed by varying paper density in a small area during the papermaking process. The image is visible as darker and lighter areas when held up to the light. Since the watermark does not copy on color copiers or scanners, it makes it harder to use lower denomination paper to print counterfeit notes in higher denominations and is a good way to authenticate the note. It depicts the same historical figure as the engraved portrait.

Color-Shifting Inks: These inks, used in the numeral on the lower right corner of the face of the note, change color when the note is viewed from different angles. The ink appears green when viewed directly and changes to black when the note is tilted.

Fine-Line Printing Patterns: This type of line structure appears normal to the human eye but is difficult for current copying and scanning equipment to resolve properly. The lines are found behind the portrait on the front and around the historic building on the back.

Enlarged Off-Center Portraits: The larger portrait can incorporate more detail, making it easier to recognize and more difficult to counterfeit. It also provides an easy way for the public to distinguish the new design from the old. The portrait is shifted off center to provide room for a watermark and unique “lanes” for the security thread in each denomination. The slight relocation also reduces wear on most of the portrait by removing it from the center, which is frequently folded. The increased image size can help people with visual impairments identify the note.

Low-Vision Feature: A large dark numeral on a light background on the lower right corner of the back. This numeral, which represents the denomination, helps people with low vision, senior citizens and others as well because it is easier to read. This feature first appeared on the Series 1996 $20 note.

Also, a machine-readable feature has been incorporated for the blind. It will facilitate development of convenient scanning devices that could identify the denomination of the note.

But the crooks, now equipped with high resolution scanners and printer, kept improving their game as well, so even more anti-counterfeiting technology got added into the currency:

3-D Security Ribbon: Look for a blue ribbon on the front of the note. Tilt the note back and forth while focusing on the blue ribbon. You will see the bells change to 100s as they move. When you tilt the note back and forth, the bells and 100s move side to side. If you tilt it side to side, they move up and down. The ribbon is woven into the paper, not printed on it.

Bell in the Inkwell: Look for an image of a color-shifting bell, inside a copper-colored inkwell, on the front of the new $100 note. Tilt it to see the bell change from copper to green, an effect which makes the bell seem to appear and disappear within the inkwell.

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