#3505 Pan American Inverts

Have any of you either sent or received the diamond shaped 80c stamps of this set as postage?

If so, do most people apply them in the intended diamond shape or position them in a square shape?

Were these the only diamond shaped modern stamps issued by the USPS?

I used one this week while mailing something to Canada. I did position it as a diamond on the envelope. This is the only U.S. diamond that I recall.
Added: Just remembered the 2003 District of Columbia stamp. So there has been at least one other. Oops ... the 1994 $5 Washington & Jackson stamp ... so at least 3 in total.
And then there are the 4 American Dance stamps from 1978 ... at least 7 total. Then add the 4 Mineral Heritage stamps from 1974 for a total of 11.

JLLebbert: You're correct! Thanks for the information on the other diamond shaped stamps. I assume then historically they haven't had any issues being read by the facer canceler system when used in the diamond shape?

Can't answer your question about the AFCS. But a quick search shows that the AFCS was first implemented in 1992. So I would think that the 1994 & 2003 issues are certainly likely candidates to have been so canceled. But I also doubt that very many of them were positioned as diamonds when used.