I think one of my latest findings fits this post perfectly:

I know it's a red "US Civil Censorship / MUNICH" machine cancellation on Czechoslavian stamp. But I'd like to know how common these are on non-german stamps?
For what I've scoured
ebay, Delcampe and other online auctions during last week, these seem quite scarce (and low value) on non-german stamps. I think I've seen only seen 2-3 similar items (all on Austrian stamps). Since this cancel is part of US postal history, I would (like to) believe that collectors on US forum like SCF have most in-depth knowledge on topic.
PS. Some information (and misc findings) about this Czechoslovakian stamp series is available on
my blog (shameless self-promotion, LOL).