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mr. mosesI didn't make the connection between the glass plates which were in the hobby a bit before the cabinets and whatever. Food for thought. The glass plates were clearly real (I passed on one at the Philly show in the 2000. range - I won 18,500. at the crap table that night after the show and bought it the next morning 
I DO know that many photographers contributed to the Old Judge series for both their actual issues and those that were entries and poses subsequently not included in the manufacture. It is not unreasonable that there are proofs NOT on cabinet mounts (I sold a small group of SMALL clearly photographers sample proofs that were unquestionably period), but today I would be wary of any such material to begin with.