Odd No4 number?

[Peter Laidler]

I agree with Amatikulu. If the original serial number was FB xxxxxA then it stays. The A suffix tells Armourers that selective fitting of parts may be necessary and the EMER note tells them this. One item that did warrant this suffix was a wider gap between the backsight ears and it wasn't unusual to see rifles with a small shim washer on one or both sides, between backsight axis pin and the ears to take up the slack