by rphillips52 » 5 Nov 2020 14:35
This appears to be an early-20C tantalus of modest quality. The lock is an imitation bramah lock.
The OP does not state whether the key found operates the lock.
Typically, these tantalus locks have 4-sliders positioned at equal distances, (i.e., 12, 3, 6, 9 o'clock) with a limited number of differs. An old-established locksmth shop, or good class antique dealer, might be able to help. Trial of keys is feasible. Fairly common to find these locks not in good order, with bent sliders, or the lock needing a clean to free moving parts.
An opening tool used for these in the past is a suitable size quill with the end cut off, and two pairs of slits at right-angles in the end of the tube. If this is pressed in gently, with a four-way rocking motion and a slight turning pressure, it can sometimes unlock the lock, and should be strong enough to move the bolt. If the the opposite slits are the same depth, and the other pair are of a different depth, because the tube is plain (i.e., without a bit) it can be tried in different positions by rotating it a quarter turn.
A game dealer or butcher might be able to supply a suitable size of quill.