yes,,,,and, no
enfield mags were hand fitted to the gun.
the tolerances are not that tight, so you might get an original or repro mag to fit and function, or.....
it's not hard to "adjust" the mag for your gun.
just remember, many no5 mk1 have bores that are pretty much shot out. they were used in multiple 3rd world conflicts, and originals are few and far between.
but a classic rifle!