Towers Double Lock w/ patented stop

Judging from the extremely helpful gallery on this site, I have a pair of Tower Double Lock w/ patented stop handcuffs. I would like to first of all make sure that these are the patented model. There is a patent stamp on them and I am able to read about 80% of it. The remainder has worn off. If I were able to open them they would stop at a certain point as a grove of metal on each end would meet. I am assuming that is what they are referring to as the "stop". They appear to be very worn and well used. I do not have a key for them and one of the locks has a key broken off in it. I would like to know what they might be worth. Any ideas? Thanks- Tiffany