( 30mm for comparison )
Land Service Anti-tank gun case
Made by RLB - Royal Ordnance Factory Birtley in 1940. Lot 414.
“CR” - Smokeless Propellant - Reduced Charge. Far more common to see “CF” - Smokeless Propellant - Full Charge.
The case has been reformed/repaired by WEX - J. Willey & Co. Haven Street, Exeter.