Flare Shell?

[pavement74]

I found this item that looks like a large shotgun shell. Appears to be live. Anyone know what it is and the time period?

 

[pointblank0]

I'm no expert, but looks to me like a mortar primer.

 

[Weasel]

It is a 4 bore shot gun shell by the look of it, if live then you should check legal status of owning or possessing such an item where you live.
If in doubt hand it in to your local Police station, best regards Weasel.