There are several levels of repair… You have to realise that rifles didn’t go back to the factory for a loose swivel screw. There is unit repair, where armourers attached to the fighting unit maintained weapons to what is now known as X level. Allows them to replace parts as required for quick turn around. IIRC, the next level repair was formation repair. The supporting REME unit would have a repair section set up well to the rear where more complex repairs could be undertaken for the larger area of fighting. Likely up to and including bolt and barrel replacement. Then there is base repair. The armourers at this level would be doing all repairs up to where the lifespan of the receiver itself was brought into question. This is the level where a master armourer would have the juice to condemn rifles to the smelter. Factory level repair, or FTR (Factory Thorough Repair) received condemned rifles and stripped them for gauging and re-use of components that passed and scrapping of components that failed. It is from the failed components that parts were sourced to assemble rifles to fulfil a contract for DP Drill Purpose rifles. Rifles in units were also periodically rotated back to the factory when as a group they were deemed to be getting close to their service life. These are the batches of rifles that were FTR’d. Not one at a time, quantities were swapped out by the unit or even more for new or FTR rifles and all of theirs went back to the factory where they were stripped, all parts gauged. Parts that passed gauging were available for re use. Parts that failed went to the smelter (or sidetracked for DP contracts) All receivers that passed gauging were then rebuilt using either new or serviceable used parts, all refinished to the level of a new rifle both in appearance and gauging. I will stand corrected on this, but to the best of my knowledge no rifle ever left the factory without the appropriate markings. If the No4 rifles were marked on the woodwork (like WW2 through to 1951 Lithgow FTR No1 rifles) and somebody has reversed something that bubba did, then the markings left with the original parts. (Happy to take MoD doc evidence to correct any of the above.)
