I did not check all the stamps issued all over the world. But let’s have a look at this one:The stamp originally issued during the tsar regime had a face value of one Kopeck. It got a first overprint after the Dashnaks took over. The 60 Kopecks (k 60 k) overprint was applied in 1920 (after the k. 60 k.was introduced in 1919). This is a rise of 600% and shows inflation was running high. Since it is type II of the k 60 k overprint (the one without the dots) the Z was probably applied at the same time. And if this is the case two different ink sets were used. The ink of the k 60 k overprint is rather diluted and a bit watery. This is one of the typical ink shades of the genuine k 6o k overprints (while it would be a sign of a forgery for other overprints). For the Z a thicker ink was used. The impression on this stamp is also quite typical. Especially interesting is the small remnant of the former frame of the Z, which was trimmed, but not completely. To the left of the Z on top (or rather below, since the HH monogram was applied later) a small stroke in heavy ink – same type like the Z – can be seen. Tchilinghirian tries to separate subtypes of the unframed Z overprints in his book and this is one of the characteristics you can look for if you want to follow in his footsteps. Finally the one Ruble HH monogram was applied. Again a very clean and nice impression on this stamp which is quite useful for comparison. Please note the tilting of the r against the 1 and the flat top of the 1. Also to the right of the ruble overprint is a frame line from the cancel device. This is often a sign of a genuine overprint. Most forgers did not bother to reproduce them.
A very nice stamp with three different genuine overprints.