For all pictorial issues exist several kind forgeries (including so called reprints). The good thing is, when you know where to look, its not too hard to detect them. This is especially useful when dealing with the forged overprints – where some numerals have few characteristics and dangerous forgeries exist. Here are two examples where the author of the catalog would not have fallen for the forgeries if he just had checked the basic stamp more carefully.
The basic stamp is a forgery. That means the overprint cant be good. The ink is wrong too (this is not easy to check with the red inks). The “1” Overprint is not easy to check – few characteristics and many dangerous forgeries. The arrows point to the place where you can easily see the stamp is forged.
The basic stamps is a forgery. Manual correction and overprint too. While the “20” overprint is quite common, the correction is not and also dangerous (while quite near to the original) forgeries of the basic overprint do exist. The arrow points to the place where you can easily see the stamp is forged.