12pdr locks/handles? ID help needed

[THarrison]

Picked these up earlier today at a fair. Not see anything like it before, any ideas what they are from? Leather on the inside of the rim (waterproofing?) and the ring rotates the screw. Possibly the locks from a storage box for explosive, not too sure.
Any ideas?

 

[reccetrooper]

What diameter is the leather section?
I’m thinking some type of tampion with the screw expanding a (missing) section that grips the bore. (Same principal as a Rawlbolt).

 

[Big Dave]

The N is probably naval issue ,QF quick firing (case and projectile together as one unit ) ,Pr12 ,13 and 3 "refers to 12 and 13 pounder and 3 inch guns ,I would take a guess at plugs for shells to be removed before fitting fuses.Probably fitting a 2" hole ?

 

[THarrison]

The diameter of the internal section (wrapped in leather) is approx 2.9 inches.

 

[THarrison]

What diameter is the leather section?
I’m thinking some type of tampion with the screw expanding a (missing) section that grips the bore. (Same principal as a Rawlbolt).

Looks ike you are correct, 12pdr gun tampions.
https://picclick.co.uk/Rare-Ww1-Royal-Navy-Qf-12-Pounder-Naval-132298907024.html
Safe to say I paid no where near that!

Thanks for the help with ID