Ahh, uhhh. That CMk.3 can sometimes be very difficult to find. It is not very sturdy, the battle-sight has a tendency to get butt-stroked off in the gun safe by another rifle being put in alongside it (ask me how I know). Probably can be repaired, IF you can find the parts. Brian Dick (BDLLTD) may have parts, such as the sight slide. A worthwhile and correct fix is to by a Mk1 (milled steel) backsight from someone like Springfield Sporters. At my last check, SS had both new and used Mk1's for sale - about $20, IIRC. Were it me, I'd buy a used one to match the wear on the rifle. $125 for that wartime Mk.1* is almost a steal. I think that the LB rifles are second only to the BSA in fit and finish. Well done!