As noted, it's a freewheel tool. The end with the pins acts as a freewheel vise or cog remover. The other end is used to hold the freewheel body (with small cogs removed), to facilitate removal of the left hand threaded, large cogs, as found on some older Regina, Atom and TDC freewheels, prior to introduction of splined cogs.

Edit: The freewheel body (with small cogs removed) is threaded into the large end. The threaded inset is then tightened down onto the freewheel body, locking it in place. so the large, left hand cogs can be removed. See item F, below.