Fiume -- CTO? what is this? anyone know anything about it?

Here's my best guess, though no guarantees. Somebody bought the set at the post office, talked a postal worker into canceling them even though he'd be walking out the door with them, and when the postal worker agreed to go along, the buyer stuck them onto the sheet of paper. I've heard things like this called "favor cancels".

Or in this case the postmark stamp itself might have been a homebrew. It looks like they were canceled on 9 December 1925; Fiume was annexed in February 1924 and remained an integral part of Italy until after World War II, when it was transferred to Jugoslavia and renamed Rijeka. (Italian is still a co-official language in Rijeka, along with Croatian.) There may have been a grace period in which Fiume stamps were accepted for postage, but that's, what, 22 months, which is very unusually long for a grace period, and I can't imagine that any post offices would have had these stamps sitting around in stock. Someone still could have brought them in talked a postal worker into postmarking the sheet, but I doubt it. It could even be that the stamps themselves are forgeries, as Fiume's stamps were forged early and often - for purposes of free & cheap postage as well as to beguile collectors.

It's certainly an interesting piece, though. Even philatelic objects of limited legitimacy can reflect something about history.

Yeah that makes some sense. Mine is a folded sheet possibly with the left edge/pane/cover cutoff at at some point.

Huh. I might have looked at that date for another few minutes and seen it that way. Or I might not. Three-digit years don't tend to jump out at me the way "19" or "1919" do; I thought 9:19 might have been the time. And I was already imprinted, so to speak, on 9 December. But on second (or sixth or eighth) glance, yeah, you got it right. I'll have to keep my eyes farther open for these varieties from here on in. (And all they're saving is a silly old 1 - that's hardly any ink at all! It's not like they have to spring for, like, an 8. You know?) Anyway, I'm glad you got the straight answer to banknoteguy .