how to tell if a stamp is valuable?

I am not familiar with stamp collecting, but the A & B suggests to me that there were two versions of the stamp printed or, perhaps, two values.

Try e-bay and put a reserve price on it so you don't have to sell it if you don't get your price.

Your stamps are probably from WWI, when Austria fought Italy. I don´t have any catalogs handy, so I can´t check now whether you´ll find them on the last pages of Austria in e.g. Michel´s catalog, or under "Italy, Austrian occupation". These military field post stamps are quite common since large ...

The 105 stamps in the 'common design' series go for less than $50 in Mint condition, actually more for lightly cancelled! - the 'individual', sometimes uniquely designed issues from the remaining colonies (which make up the other 100 or so) are rather more pricey - I would estimate at least $200 or ...

Anton Bruckner is an Austrian organist and composer of romantic music.

Thank you...I will try those things