Thanks perf12 and floortrader. Sure, I was instinctly drawn to the eagle, which looked like taken straight from the Polish emblem. I must say that the smaller Tirol one looked similar.
It has Tarnów 1 cancel, with invisible date, very light. Under big magnification I cannot confirm what I would love to believe, i.e. that it is legit. It's the first time I am dealing with a bogus item - a learning curve.
Thanks perf12 for the links. I am into Southern African and African stamps (spent 27 years in SA), but
inherited 30 albums from my father, mostly European stamps. Cannot quickly discern what could be valuable or not, what could be potentially fake and so on - do not have a good eye for it, struggle with that mass of stamps

Adam