Overprints and surcharges, which are a subset of overprints are one of the most problematic areas within philately for two reasons:
- Many of the world's rarest stamps are common stamps that have been overprinted.
- Many overprints have been extensively forged, due to the difference in value between unoverprinted stamps and overprinted stamps.
The quality of the forgery work on overprints varies from extremely poor overprints that look nothing like the originals, to extremely good forgeries being made with laser printers and other specialized equipment. Consequently, certificates are a must for a lot of more expensive overprints.
But what about less expensive stamps that are not worth the cost of a certificate? Fortunately there are ways that you can learn to spot forged overprints. The best way to explain how to spot the differences is to go through an example. Look at the two Canada #O9 50c Lumbering stamps with the scarce O.H.M.S. overprint shown below:
The overprint on the left is genuine, while the one on the right is a fake. How to tell the difference? Even without a closer scan, you can see that the "O" is thinner at the top than the genuine stamp. However there are other differences, which can best be seen by looking at each stamp close up and comparing the differences.
Let's start with the genuine overprint:
The overprint measures just under 15 mm from the left edge of the "O" to the end of the period after the "S". All letters except the "O" are just over 2 mm tall, while the "O" is 2.25 mm tall. The "O" is narrower at the top and bottom than it is on the sides, but both the top and bottom and sides are of even thickness. The right diagonal stroke of the "M" is very thin. The periods are ever so slightly elliptical in shape, and are all the same size. Finally, there is a light impression in the paper, visible from the gum, of the entire overprint, caused from the impact of the overprinting die on the stamp during printing that looks like this:
Now, let's take a look at the fake:
This overprint also measures just under 15 mm in width. The letters are all 2 mm tall, so that the "O" is slightly shorter than it should be. It is also too thin at the top and bottom. The right diagonal stroke of the "M" is thicker than in the original. Finally the periods are not quite the same size, with the period after the "H" being slightly larger than the others. They are also perfectly round and not slightly elliptical as in the genuine. Both overprints have ink that looks shiny when viewed at an angle, but the ink of the forgery looks flatter when viewed dead on, compared to the genuine. But the final tell-tale sign is that when you turn the stamp over, there is no impression of the overprint at all:
You see? Nothing. Which means that the printing was done by a very low impact printer, not by an industrial printing press.
This is a particularly good and dangerous forgery that came from e-bay back in 2011. There was a ring of sellers between 2010 and 2012 that were selling these overprints on many Canadian official issues, in quantity, week after week. It is thought that they used a laser printer to overprint full sheets of less expensive stamps, and that they used Photoshop to replicate the overprint. As you can see, they did an excellent job, but even so, with careful comparison and examination you can tell the difference and avoid getting taken.
So the basic lesson is this:
- Learn the exact dimensions of the genuine overprint, including the length of the overprint, the height of the letters, and the spacing between lines of text and letters.
- Examine the ink of the genuine overprints carefully and note how it appears when viewed straight on versus at an angle to a light source.
- Note whether the overprinting usually left an impression on the stamp that can be seen from the back or not.
- Carefully examine the colour of the overprint ink and compare to a known original. Almost always, the colour will be slightly off.
Quite often it is difficult to obtain a known genuine example of an overprint, in which case you will need to consult specialized literature that will give you the information about the genuine overprint that you will need to make the comparison. However, such literature is generally available from sellers like Phil Bansner, whose link appears on my page titled "For Further Reading - Other Cool Websites".