Depends on it's accessibility. I use 4 1/2" angle grinder with thin metal cut off blades. They wont cut all they way though from one side so accessibilty around the pipe helps. I have a thread showing how to cut through if it's in a wall or you can't run the grinder around the pipe. Let me go find it and I'll link it.
Thanks for the reply. I have good access so cutting would be no problem.
I am wondering if I hammer on the flange with a block of wood or just hammer would work? I have no idea how hard 86 year old lead would still be holding.
I would like to just put the short piece back in again. I want to remove it to clean the bell end, the lead toilet bowl flange is coming apart.