Check to see if the stamps are engraved or lithographic...

Rubbing the stamp with foil over the top will tell you...
* Engraved will leave an image on the foil
* Lithographic will not
If lithographic, check to see if it is the Vienna issue..
The Hellas2010 catalogue on pages 150-151 give several differences.
One of the differences is the Vienna 1 drachma value will have delta and P, and the M and H script touching each other toward the bottom of the lettering, while the Aspiotis issue will have these letters with separation.
Can you tell which one you have now?

