http://www.iwmcollections.org.uk/med...e/H_005865.jpg
You have seen this photo before. I purchased a print from the IWM. It is of a 12-pounder mounted on the back of an Albion 6 x 4 (1938? WD131?) L 2511542 in 1940 at Fort Horsted, Chatham on 1st December 1940 from the batch : L 211502 to 212001, to contract V.3560: 'Lorry 3-ton G/S, Pontoon, TSR, Folding Boat Equipment, LLB, SBG, Break Down'.
Excuse my ignorance but what does TSR, LLB, and SBG stand for? Also, was the 12-pounder a naval gun originally?