Can anyone ID this copper ELEY object?

Someone I know got the following with some other various rounds.

It is a copper object around 8mm across at it’s widest point, with a 23mm Length.

The end is open and is sealed with some sort of Shellac sealant.

The front “cone” is marked “ELEY” so it must be cun or cartridge related.

See MS Paint drawing below.

Thanks for any info.

It is a “Percussion Shell for Conical Bullets” as per an Eley Bros London labeled tin. Made in at least two sizes and found with a raised ELEY & unmarked.

These are found in some hollow pointed .577/.450 MH bullets and sometimes in the Jacob hollow point bullet.

In effect it makes the bullet explosive.

Thanks Pete, Great info.