You've been in the Army RAE......... Like your plant and equipment, once the rifles have come from Ordnance, bright and shining new, after a year or so they're used and starting to get a bit tatty. So they go into workshops for a bit of TLC and so on. After that they go back to the unit and so on. That's what I mean! It can only be facory new ONCE. Thereafter, it's rebuilt in the RAEME Armourers shop or sent back to a Base Workshop where it is rebuilt to brand new spec again, probably several times in its life just like the SLR you were issued with. That was made in 1973 but you had it like-new in 1993.
As a matter of interest, just because the barrel is a bit rats, nowadays, this doesn't count too much. What DOES count now is the bore gauge free run (.301" MUST run freely in your case) and more importantly, the functioning and accuracy test.