Mystery Object - fits a No.4 barrel?

[WillSarchet]

My two. A G.E.S. 2 marked one and an Enfield marked brass one. The "2" does not fit a No4 barrel - won't close on it - but it does fit a No1 muzzle snugly and lives in my No1 tool drawer. The brass one is larger, presumably for a Martini-Henry but I keep forgetting to test that.

[Warren]

The brass one will fit a Vickers barrel
I have one attached to my .22 Vickers sub calibre unit.