Looking at signatures for Armenia, and several places mention a “National Bank of Armenia”, predating the current central bank.
If that's the case the Central bank was opperating from 1993 to date
The National bank operated from 1991-1993.
Since I'm not able to read Armenian, I can't tell if the lettering is significantly changed, but I think the split in banknotes would be between either P#38 and P#39 or between P#40 and P#41.
The first is bassed on the start of operation at the Central Bank
The later is based on the end of the first series of Dram notes.
This can couse a little trouble with the banknotes of the past, the rouble notes. Most of them, if not all, seem to have been issued by: Erivan Branch of Government Bank, but can't really find any information about it.
What are people more knowleadgable then me's opinion? :D
Sources:
https://www.moneypedia.de/index.php/Signatur:_Armenien
https://en.wikipedia.org/wiki/Central_Bank_of_Armenia
http://www.banknote.ws/COLLECTION/countries/ASI/ARM/ARM.htm
SCWPM, modern issue, page 64
SCWPM, general issue, page 56
