I ran across this at a local FM on Wed. I don't normally pay $4 for 6 in. adjustable's, but this one was different enough to warrant it.
I had a 12 in. Craftsman with this same type of lock that I traded to my FIL about 30 years ago. I haven't seen one since. This one, as you can see, has the name etc. stamped into the handle, which indicates to me that it may have been made for different companies under contract. It seems to me that the ones with the name etc. forged into the handles were probably made by that actual company for themselves.
Pushing on the adjustable jaw end locks the adjusting knurl, and pushing on the other end unlocks it. I assume this is a Grainger item because of the Dayton name.
I would imagine that it was patented, but I haven't found one yet. Anybody know what it would be.
Mike