Thanks Both! I've taken a few more photos here in natural light - hopefully that shows things more clearly. BigDuke - those are S's rather than 8's used for the cancelling - should be clearer in the new picture. I have seen an article on similar in the last 6 months which I must track down. As Roger pointed out though - that could well have been civvie renumbering rather than military. Also included a more clear view of the bracket number - the zero's are only partially formed so hopefully that might point to sloppy armoury numbering rather than a civvie gunsmith! ;-)
Roger - no makers stamps (JG or similar) that I can see on the bracket. Interesting (and I hadn't spotted that before) is that the forward bracket screws have been restaked, so the bracket could well have come off a different rifle? Put up a clearer photo of the number/fonts for the butt as well. Haven't spotted anything unusual on the other stamps on the receiver - just the Mk1* designation and the T. Only other marks I can see on the bracket are the expected collimation numbers on the rings.
Also done a close-up on the new number, and you should be able to make out the FTR characters under it.
Any further thoughts or observations most appreciated!