Thanks for the ideas so far. I should have mentioned, there is no locking cutout on the socket. Only the notch in the raised rim of the socket base showing in the second picture. This rim does not go around the entire base of the socket, but raises gradually from the bottom. It appears as though it took a “one-quarter” turn of the bayonet to lock it into whatever fit into the notch.
Also without a cut out, this would have to attach to a rifle barrel in front of the front sight. If it was equipped with one.