Look at the seating stem plugs ...
Like Ivan noted ... one is prpbably for a round nose bullet and the other could be for a semi-wadcutter .
Another possibility is one applies a Taper Crimp and the other die applies a Roll Crimp ... for 45 Auto-Rim loads .
The problem buying used is you don't know what the previous owner was doing . My 45 acp dies have two seating and crimping dies ...
I I Seat the bullet in the first step and Crimp the bullet in the second step ... I find Seating first in one and then crimping in a seperate step / die does a better job .... and Might be what the original owner was doing also !
Good Luck finding the answer ...
post what you discover !
Gary