Postally Used Proofs?

Can proofs be postally used? I'm asking because I found an auction lot of postally used United States classic era proofs (so they say) Some look as if they are just trimmed regular issues but I have been wrong before so that's why I'm asking? Thank you.



http://www.ebay.com/itm/10-Differen...em41683f2073

I think you called it right. Looking at the margins on those, and assuming they are all on stamp paper, the only one that has any chance of being an imperf on stamp paper is the 210 in the bottom row. Good luck to anyone trying to get a cert on that. The rest are all carefully trimmed stamps, some of which had larger margins from being in the outside positions on the plate. Before trimming some of them would have been nice jumbos, even if not well centered. Too bad.

If it walks like a duck, quacks like a duck . . . it's a duck. These are some of the duckiest ducks I have seen.