I actually thought this to be a pocket watch chain. But it has a patent number 2048599 that shows it was an improved device for holding keys in such a way that they were held side by side and would fit into a pocket easier than a circular one. The patent was filed by J.M. Collins 4-11-1935 and was awarded the patent in 1936. Also stamped 1/40 12K I.R.G.P. and has a markers mark Cor Ect in a pyramid shape. The tension clip slips over the outside seam of a pocket opening with the long chain hanging down and the keys into your pocket. I can see this also being used for attaching to wallets that have a riveted ring, watches, or lockets. In great condition with light wear and no gold loss, just some light tarnish from age and a few light scratches. Total length is 19" and weighs 16.6 grams. Great piece!