Snap On L-73 with Snap On factory modification
also stamped N-3325
Patent no. 1854513
1952 date code
The L-73 is normally a 1" drive ratchet head that attches to a round bar handle. This has no hole to attach to a handle.
Instead, there is a 1" drive female square on back (socket-like construction complete with socket release button) for an extension, t- handle, breaker bar, etc.
Not sure if this was designated as a ratchet or "ratcheting adapter" because of that.
I have seen a few of these but their specific application, if one, is unkown.