The only single star stamps I’m familiar with are French or Spanish but not at all for this type of firearm.
Odd that they are on the tops of the barrels too.

Anyway, I agree that a 500No.2 is more fun than a 450 but I don’t know if it is more or less desirable to the majority of collectors.
450s being much easier to source dies and brass etc.
I have had success with this cartridge using black and smokeless - it seems pretty forgiving.