Another Grenade - Marine Artillery?

[Harry Man of Kent]

The larger grenade here I can't identify, it was also in the Marine section of the collection I am going through (see me previous RMA post) but it doesn't look like a Marine item to me. I have put a normal OR RMA grenade beside it for scale. Two lugs to the rear, reasonable quality & looks like it was gilt but rubbed through now. I would be grateful for any thoughts.

[btns]

size matters!