The above is a printed-to-private-order (PTPO) envelope, with the indicia/stamp images printed by the government printers. Mailers could use their own custom or imprinted stationery with nobody needing to lick and stick stamps. Other countries did this too. Of course, the buyer had to pay printing costs and the postage value. The indicia/stamp images here are the same size and color of issued stamps. PTPO Austrian stationery is listed in stationery catalogs.
These were initially sold as whole envelopes, I think with a sizable premium over face. There is no doubt in my mind this was intended to sell to collectors only. Fraudsters obviously like these.
Here's one that's just as bad or worse:
All 3 values of the 1949 UPU designs on what is presented as a gummed mailing label with postage. Again, they are the same size and colors as the issued stamps. Cut apart, they are then offered as "RARE IMPERFS". Not. There is a PTPO aerogramme with all 3 values also; I think another similar item exists. Unfortunately, spaces for this stationery (and no other) were given on (Minkus?? White Ace??) 1949 UPU album pages.