This is an old style wad-cutter that still has a useful purpose.  The other two wad-cutters are generally loaded flush with the case mouth. This one is loaded with the button above the case mouth. You will always be able to see that it is loaded ammo. If you are loading ammo in a machine with a case feeder, and a live round still has a bullet in it that is seated flush, it will likely feed upside down and expose the live primer to the decapping pin. This one is likely to fall over if it ever feeds upside down. And it shoots very well.

Don't mix live ammo with empty cases.