I hope this is allowed , I came across this Cable Release while sorting through some bits and pieces..But I have no idea what it is Supposed to Fit..it is 8 inches in Length Has Germany Stamped on the End and I think the Metal is Nickel..the hard Plastic - Bakelite end - fitting is not Detachable ? The end bakelite fitting is 1/2 inch unthreaded.
As Chuck1 said, it is a cable release for a Polaroid camera, probably a folding packfilm camera, most of these had plastic bodies and a large shutter button. It's likely part #191 , if you google Polaroid cable release you'll find more images of them.
That is interesting and thank you I have some Vintage Polaroids Folding Type , I will Dig them Out and see if they fit, I found a release on a certain web site that is the same..