See picture: http://picasaweb.google.com/craig.conboy/BeachFind...

I have found a few of these washed up on the beach along the St. Lawrence River. Metallic. Curious about where they come from and what they are used for.

Thanks for the thoughts! There is no sign of threading in the hole, and the hole is a pronounced ellipse not circular. So perhaps the lack of threading and distortion are the result of many years polishing on the beach? Are lock rings something that is used on sailing or shipping vessels?