You used to be fairly safe buying an orphan (non-matching) Navy magazine, why would anyone take the trouble to fake one? Well now they do. There are two glaring red flags on this one, the rectangular stake marks on the tube, indicative of Erfurt manufacture, and the closed number 4 on the base, an absolute no-no on Imperial Navy mags.
Norm
https://www.ebay.com/itm/184381378108?ul_noapp=true
Norm
https://www.ebay.com/itm/184381378108?ul_noapp=true