Managed to have another peek at the 1941 Fazakerley again, this time with a No.3 bolt head and some calipers. Like an idiot, I measured the bolt head length of the #4 bolt head but forgot to write it down. I did swap out the bolt head for a #3 (length 0.635") and the rifle only just failed (As in I could detect slight pressure, but the bolt still closed). I think if I can get hold of a #3 bolt head that is slightly longer but within tolerance (i.e. closer to 0.640"), it might pass the field gauge. On closer inspection, the rifle appears to be original with no import marks. The rear hand guard, forend and buttstock are varnished, but that isn't difficult to deal with. The forend is one of the early ones with the low right hand wall, and there are some stamping under the varnish on the buttstock that I can't make out due to the varnish.

I know I asked these questions at the beginning of the thread, but I still haven't found any answers, so I'll try again :P

1. When was the Mk.II rear sight introduced to Britishicon rifles?
2. When was the Mk.II cocking piece introduced to British rifles?
3. What type of upper band should be seen on an ROF 1941 No.4 Mk.1?

Just so you know, I spend all day asking questions and not stopping until I get answers - it is like being a 4-year old all over again...