Curious "8x10 bromide" plate holders
I recently purchased at auction a lovely 8x0 Eastman View Camera 2-D (Folmer Graflex manufacture)with a lovely Crown No. 4 tripod. The lot also included a number of film and plate holders of various sizes and types.
One interesting item was a set of four plate holders marked "8x10 BROMIDE" on the top edge and "FOLMER GRAFLEX CORP U.S.A." on the bottom edge.
The holders are single-sided, with a conventional dark slide on the live face. The back has a paneled door that opens on hinges, with two very nice slide locks - all hardware chrome plated. There is a little leather tab, held by a chrome-plated plate, to use to open the door. The holder body is an ebony back.
The plate recess is exactly 8" x 10", and each unit one includes a wood adapter to receive a 5" x 7" plate. (And there were 5x7 sheets of film held in those with masking tape!)
The holders are not the same size as a conventional Graphic-type 8x10 film holder. They are 9-5/8" high (vs. 9-5/16" for the conventional holder) and 12" long to the point from which the dark slide emerges (vs. 11-5/8" for the conventional holder). They have a locating/light seal rib rather wider than on a conventional holder and located nearer the end.
Also included was an even more curious item. This is a wood frame obviously intended to go into the camera back in place of the plate holder. It carries a glass screen, but a clear one (not ground glass). The screen is held by four clips at the edges just as we might find holding a ground glass plate into a spring back focusing plate assembly. The glass has "clipped" corners.
The clear plate has at its center an engraved "crosshair graticule" in the form of a cross 2" x 2" in overall size. On the "south and east" legs it carries marks at a spacing of 1/5", and on the "north and west" legs has major division marks at a spacing of 1/5" with minor divisions at a spacing of 1/25". (It may be that the intent is for these to be at 5 mm and 1 mm pitch; the spacing is a little irregular so I can't determine that for certain.)
This item carries no markings, but the ebony finish on the wood, the chrome plated clips, and the consistent dimensions suggests that it is a companion item.
Someone has suggested this this is fur use in aerial image focuing technique.
Does any one know just what these might be and what kind of camera they were intended for use with?
The holders for glass plates I also found out are not the same external dimensions as the holders for same-size cut film, and thus won't fit onto modern or antique cameras designed to take cut film holders.