Just when I was beginning to think there would be no more surprises I pulled this Latvian stamp out of one of the albums I got last weekend.

When I turned it over I found this...

...printed on the backs of unfinished banknotes, according to Scott's, "of the government of Colonel Bermondt-Avalov and on the so-called German 'Ober-Ost' money". With surcharge 1921 (SC#97).
Pretty awesome. But of course there's a footnote that excellent counterfeits exist.
Someone please tell me this one is legit. Finding too many counterfeits in this stash.