Vintage Apollo ferrotype plates, chrome plated steel mirror sheets, lot of 4

Lot of 4 vintage chrome plated steel ferrotype plates... These are 10 inch x 14 inch steel plates, chrome plated and polished to a mirror finish on one side.

These are vintage dark room equipment for producing glossy prints. Two of them are marked Apollo and the other two are marked Kingsley.

These plates are new old stock and three are still in their original paper envelopes (the 4th has lost its envelope over the years).