I just bought these printed portrait frames, which consist of a glass back with a paper print stuck to the front.
They appear to be negatives as the printer's name - "C.E & C Reg" is reversed in the corner of each.
Does anyone recognise or know how these were originally used?
I'm thinking putting one in a frame and doing a contact print, then exposing a photo in the oval or rectangular space.
I haven't done a contact print from paper to paper before but I guess that should work out ok.

Actually, just came across this:
which is what I'm expecting the final result to be, so I guess I'm on the right track!