No 1 Mk III mag MOD'ed to fit 4's or 5's

There is a mag for sale that proports to be a modified Mk III mag to suit the 4-5 was this ever carried out or is it just another back yarder, below copied from the fleabay ad

Lee - Enfield Conversion Magazine 10 rd. FOR No. 4 or No.5 “Was a No. 1 MK III 10 rd. Mag converted to fit the No. 4 & 5's in the late 50's”

Anyway those of you in the know will expand the knowledge of us fledglings. :rolleyes:

1000s were converted during WW2, even the No7 has a converted SMLE magazine

I've read in Skinnerton's book that 20,000 were converted in 1941.

Somewhere I have a picture of three types of mags, No 1, No 1 Converted, No. 4.
I'll look for it tonight.