Quote:
... it is one of the few precancels from Pennsylvania that I've seen which uses the "PENNA." state abbreviation.
Is this example unique or common for that period?
There are a quite a few other towns with local precancels using the old "Penna." abbreviation. There are also a few that use the even more archaic "Penn'a." form. "Warren, Penn'a." is listed at $2 in the catalogue, "McKeesport Penn'a." at $5, and the others are all at least $50. So, that usage is one that might be tough to come across.
Ryan