I like postal stationery.
I collected stamps as a kid, focusing mostly on US stamps.
These days I'm drawn more to Air Mail stamps and postal stationery, meaning, those embossed envelopes and pre-printed postal cards. And then of that group, I prefer pre-1970 stuff.
I picked up a bunch of entire envelopes on Listia recently.
1956 UC25 6-cent FIPEX Commemorative Air Mail envelope with UC31 1-cent surcharge.
470 credits. I then won a second one a little later for only 3 credits after just 2 bids.
1962 UC36 8-cent Air Mail envelope.
8 bids, 402 credits.
1958 U536 4-cent Franklin envelope with U545 1-cent surcharge.
6 bids, 301 credits.
1968 U551 6-cent Liberty envelope with U561 2-cent surcharge.
3 bids, 402 credits.
Also grabbed this little beauty:
A 1971 Topps Johnny Bench.
A bit trashed but after 22 bids I got it for only 2020 credits.
Paper missing on the back...but again, I didn't have a '71 Bench and now I do.
And it cost me no dough.