There are lots and lots of times when I really do just have to guess at what it is I have. This is one of those times. There are a few clues, which the two cabinet card photographs present to me outside of the simple fact that they are Victorian era cabinet card photographs.
This first was taken at "The Penton Studio" in London. A lovely portrait of a young Victorian woman. The photograph is not flat, but rather a kind of a square 'bubble' mounted on the card.
The second photograph, also taken at Penton Studio, also has this 'celluloid-like' square bubble with just the outside edge of the photograph glued down to the card backing.
I think you can see what I mean in this third photo.
On the back of this card (the first card has a blank backing) is wording which leads me to believe that their are negatives for this photograph: "Copies may be had at any time." This eliminates this being some form of tintype and makes it a process which involves negatives. But what type of process? So far, I have not found any information online which gives me more than I already have here....
Have you come across this type of photograph before? Any light you could shed on this would help me, and likely others as well.