I think it's a wad seater for the 410 shotshell.
A 'Tamper' they are usually called and they are generally paired with a brass 'Filler Tube' which the hull being loaded is placed inside while
all the components are put in one by one and pushed down firmly with the Tamper/Wad Seater.
Could be a 'Starter' for a M/Loader.
It wouldn't be one for use w/a False Muzzle with that flare machined on it.
If it is a Starter, the end shape could certainly be for a round ball just as much as for a bullet shape projectile.
At it's length, it'd be a Long Start. If using one, the shooter would generally need a 'Short Start' as well. Usually both are combined into one tool for the field to make things handy.
Interesting things you find in boxes of 'stuff'!
