Paint Behind Glass - 2 Pieces in Mill Bay, British Columbia for sale

Two pieces of art that I believe are paint on the back of glass. They are very old and I do not want to damage them checking. Both pictures describe in detail [at the bottom of each painting] the names and details of the sales of specific horses in or around 1795. They are framed in what I believe to be hardwood frames with 'birds eye' maple veneer. Some of the veneer is beginning to peel and though it is not perfect, both frames are still beautiful. A few drops of glue will secure any peel, but I don't want to mess anything up by risking a bad job. Both pictures are being very carefully handled.
They are perfect for older homes and once hung in "The Grange", a Samuel McClure mansion. They are beautiful pieces of art and will be sold as a pair. $225 for both.