Similar answer to that in the Spitfire question I'm afraid. With OTUs, the problem can be more difficult than with Squadrons, as aircraft were (relatively) quickly turned over, with 'tired' replacements coming from the Squadrons a, and, after major overhaul or repair, from the MUs. If you have the Mark, you may find the answer by a process of elimination, by searching through the serial blocks. I would suggest that, being four digit numbers, these are probably the Mark 1, possibly from the N or P serial blocks, but that's certainly not positive.