Counterfeit Detection: Duplicated Serial Number

Sometimes when a banknote is being printed, a problem may occur — too much or too little ink may be applied, one pass may be inverted, the sheet may be folded or torn, etc. While problematic for the printer/mint, these mistakes produce interesting and unique banknotes for collectors, and they can increase the value of the piece.

One possible type of error is a duplicated serial number. While serial numbers are supposed to be unique, occasionally a malfunction will cause the same one to be printed on two separate notes. PMG will grade these errors, provided the customer sends in both notes at the same time… and provided that both notes are genuine. Unfortunately, this is not always the case.

Genuine Friedberg #607 Click image to enlarge

Counterfeit Friedberg #607 Click image to enlarge

The above two notes (Friedberg #607) were recently sent to PMG for grading. While entering the note information into the system, the research team noticed that the notes had the same Friedberg number, charter number, serial number, and plate position — a perfect example of a duplicate serial number error! However, closer inspection showed something odd…

Looking closely at the notes, the graders could see that the serial numbers weren’t the only things that matched: wear, stains, and even some fibers were identical from one note to the next. Under high magnification, it became obvious that the second note was actually just a photocopy of the first, and all of the blemishes that original note had acquired over the years had been copied over, as well.

Genuine (left); Counterfeit (right) Click image to enlarge

Genuine (left); Counterfeit (right) Click image to enlarge

Genuine (left); Counterfeit (right) Click image to enlarge

Genuine (left) and Counterfeit (right) under a specialized light source Click image to enlarge

In the above images, taken under a specialized light source, we can also see a difference in how the ink reacts. The image on the left show the genuine note, with its fibers fluorescing brightly, and the rest of the note showing as a fairly even gray color. However, the image on the right shows many small dots fluorescing, instead. This reaction is indicative of inkjet printing, in which tiny dots in three colors of ink are printed and combine to create all other colors on the paper. The different colors react differently to the light source, causing some of the spots to fluoresce while others stay dark.

If there was ever any doubt that the second note was a copy, these images would be the final nail in the coffin. In the end, the original note was graded, while the other was returned as counterfeit.

As always, any notes graded by PMG are backed by our PMG Guarantee of grade and authenticity.

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