I have found many of these they are silver plated brass, and are decorative strap keepers from horse bridal/tracks. They were very decorative and being shipped back to Spain from the new world.
Yes. The rings are a real mystery still. This is the third one I've found , all are slightly different in shape, but all have the rope border feature. I know of five like this that have been found here all with the rope border. Usually find coins with them too !! Wooo hoooo !!