With great thanks to Graham (GeeRam) for pointing out that there was specifically the rifle I wanted on MFLClassicFirearms almost 2 weeks ago, I am now the proud owner of...

A 1947 BSA (Shirley) made No. 5 mk. 1. Matching serials.
I am over the moon. Aside from the massive journey to go pick it up, it looks lovely and I can't wait to get out and put it through it's paces.
Picked up 100 rounds of PPU whilst out there (and the sling), so just need a day at the range to blow the cobwebs out of the old girl.
It's also got, which I love, remnants of a painted number on the stock, presumably for rack identification in a military stockroom somewhere?

What it's got on the bottom, that I'm hoping some of you guys can tell me more about, is some numbers on the magazine, that have got XX's through them, presumably nullifying them. Can anyone give me more info on what they were? was it a previously issued magazine to a different serial number, then it got serialised to my rifle?
Anywhoo.
Much happy. please let me know if the picture doesn't load and I'll adjust some settings.
TG :)