It's Greece, Scott catalogue number 376. The basic stamp is actually #336, 3 drachma dark blue, issued August 1st, 1927 and depicting General Charles N Fabvier. It is one from a set of three commemorating the centenary of the liberation of Athens from the Turks in 1826. This one and one other value from the set were surcharged (i.e. overprinted to give the stamp a different value) in 1932. Yours was surcharged with the value of 2 drachma, and the 6 drachma stamp was surcharged 4 drachma. The postmark looks like Salonika.