I bought this ususual shaped lock at an antique store over 30 years ago and have always wondered whether the design has a known functional purpose or if perhaps it was just a "master piece" made by an apprentice locksmith as part of his "final exam" to become a master locksmith.
(Hmm, I wonder if that activity could be the origin of the word masterpiece? I leave that question to any entomologists here.)
Here 'tis:When closed, the OD is 3-1/4", ID is 1-1/4", and it's 13/16" thick.
The half with the tongue on it appears to be one solid piece, the one with the keyhole and locking parts inside it has a barely visible joint line halfway up its thickness, it's held together by several rivets.
There's no name or other markings on it.
The only application I can think of for this gadget is that it might have been locked into a groove cut in a shaft, to secure something in place.
Anyone know a serious practical use for this type of lock?