should have noted - the die body on the left is a 44mag or other expander die- maybe .45/70 - they're all the same, except for length. The 'plug' is a .45/70 RCBS plug, tapered to go into .35 Whelen or larger cases.

The die body on the right is a shortened .300 Win Mag. that I bored for neck sizing 9.3x62's- perhaps 30 years ago. I turned the plug for it out of mild steel, threading 10/32 or 8/32 for a normal RCBS decap stem. Either plug works well.