Posted By:
warshawlawWhile looking over the backs of some new 1925-29 PC Back Exhibits I just received I noticed that one says "not to be used in exhibit machines" (just like every other one I've ever had) while the other says "not to be used in exhibit machine". Since both make grammatical sense, there may be a legitimate variation.
Does anyone else have one of these cards with the singular "machine" on the back?