I have an old blacksmith vice that has a few features that i have not been able to identify the purpose. The vice was from my grandfather who worked for the railroads in Chicago from the 1920's to the 1950's The vice hand crank is mounted on a shaft that if the assembly is slid forward, it will rotate and close the vice jaws. If the assembly is slid back, the hand crank can rotate a set of gear that spins a cylinder below the vice jaws (see pics). The cylinder has a 0.50" bore, but is not lined up with a hole on the opposite side of the jaws.
Any thoughts on the cylinder purpose? .
Thanks in advance