I have a couple of family ones. (Not in this house or I would photograph for you.) The ones I have are just head and shoulders and are behind glass, with an oval filet. If they were the full size of the frame they were often without glass. You really need an old frame with some depth to show them off properly - often you can buy these these cheaply at real-life auctions. I have added 2 photos of a couple of examples I sold some years ago - they can be very attractive. In my opinion the 2nd one of the lady would have looked better with an oval filet around. They are of course extremely fragile. And so often did not survive.
Actually the second frame would have been lovely once - covered in red plush velvet, but battered by the years. They are just a single sheet of milk glass, and are VERY fragile. I am sure breakage occurs in re-framing, probably from someone leaning on them, or putting a nail in the wrong place. If it were mine and the frame is OK, I would leave well enough alone. The ones I have re-framed, I put behind glass, using a mat to go between the glass and the opalotype, - I used the wrong term in my previous answer. I have attached some closer pics which show the images outside of the frames - I think they are quite lovely. The close-up portrait has a lot more hand embellishing, as my family portraits have. I think it would look much better with an oval mat. As you can see, the original plush frame had a gold fillet. The young girl just looks to be a straight studio portrait. You can google lots of info on the process; my photography research books tell me it was most popular in Australia 1880-1900.
