Checking the head/barrel configuration, I have:

Front Cyl; Head has "KV3L FR2" cast into it; Barrel has "H1" cast in the circle on the bottom left side, is stamped "B" at the back, and has "0YH2 319" stamped along the base on the RHS.

I take this as an SP head on an R barrel, not the best setup....But it should be OK so long as I only run high octane premium ULP correct?

Rear Cyl: Head has "KV3 RR2" cast into it; Barrel has "L1" cast in the circle of the bottom left side, is stamped "B" at the back, and has "2MJ IL 106" stamped into the base on the RHS.

This I take as an SP barrel with SP head.

Both cylinders are "B" grade (and will take 'no mark' pistons).

Can anyone tell me what the code stamped in the base of the barrels is?

I have noticed some other things that are very unusual and will definitely require the assistance of the more technically minded NSR forum readers.............