What was this 1.2-inch Plug used on?

[Depotman]

The only two items I know of with a 1.2-inch thread is the ‘standard’ primer introduced for many WW1 brass shell-cases (e.g. 13-pr, 18-pr, 4.5-inch How, and a number of Naval cases).

The stampings are very clear – so, ideas please!

Depotman

 

[TimG]

Trevor,
You're looking at the wrong end!
2Pr Transit Plug.

P 1.2 II N - Plug 1.2 inch Mark II Naval
J.S. & Co. - John Smith & Co of Derby (most likely) https://gracesguide.co.uk/John_Smith_and_Co
Pb - presumably denotes it is non lead free
TL within lozenge - significance unknown to me

TimG