This is a full sized 8x10 holder for glass plates - with inserts to allow use of 5x7, 4x5 or 3 1/4x4 1/4 plates as well. The inserts are removable so you can vary the size plate used. Two I have sold in the past years have been used by wet plate workers. Another said he could not figure it out. So, if you have no knowledge better pass on this one.
Fits a regular 8x10 camera back. If you have wanted to try wet plate, glass plate or tintype work this might be what you need.
$150 plus shipping and I'm located in the US