Help with ID/purpose please!!

[hicky1300]

Hi Gents
As the sort out is drawing to a close got a few rogue items in the collection still!!
On the left is a cut down 2 pounder case. Headstamp is N (navy) 1941 2Pr No1 MKII ECC
This is 71mm tall & the internal diameter at the top is 34mm.
The taper at the top appears to have been done properly - namely drawn or spun as thickness of material is uniform & it is very round.
My feeling is a blank or charge for depth charges or something?
The projectile in the middle is 2 1/2 pounds in weight, is 150mm tall & has a diameter of 43mm (1/1/2"). Grooves for 2 drive bands.
End projectile is a 37mm but the drive bands have me stumped?!. It is also hollow with an internal thread in the base but I think it is too much space to have been purely for tracer - base fuzed HE?? It has 2 stampings above the top drive band one is a bunch of grapes (NOT a flaming grenade) the other looks like a crown over a 7 or an `M`??
Ideas as to age/origin/purpose appreciated.
Thoughts on postcards to BOCN please!!
Thanks, as ever, in advance

 

[hicky1300]

Sorry just to add: the middle proj is solid & appears to be of hardened steel (AP?)

 

[Gspragge]

The right hand one is a German tracer, nice fired example. I show the type in my album.

 

[charley777]

Greetings , the case on the left is a 2Pr No1 that has been modified for use in the Hedgehog anti-submarine depth charge thrower. I include images of one that was purpose-made. There was a cardboard extension, like a shotshell, and ignition was acheived electrically by a wire inserted in the open end.