But Hardinge did not make chucks and a number of chuck companies did make chucks and adapter plates to fit Hardinge lathes. Late model chucks for Hardinge lathes are mostly either 5" or 6" diameter. That pin will not necessarily fit them all. I will take a guess and suggest the threaded pin is most likely to fit a chuck with a little round name tag that says Hardinge by Buck, but I cannot guess if it might fit the 5" or the 6" or both.
So it might help someone thinking of buying it if you post some dimensions.
Larry