Mk. I - has the separate bolt release catch, not the cutout in the guide rib like most North American No. 4s. Made 1941 at Royal Ordnance Factory Maltby, refurbished at Fazakerly in 1947. Fultons would have set it up for target shooting after that. At the time they breathed on it, it would have been a sound rifle, they wouldn't have wasted their time on it otherwise. If the bore is dark, that happened later, not when the rifle was being used for target shooting. Target rifles can have eroded throats, from a lot of shooting, but are otherwise clear. Does it have a centre swivel just in front of the magazine? It probably would have had a PH5C or similar sight fitted at one time. With the Fultons mark, it would be appropriate to install one. Cross your fingers, the bore might just be fouled. Bought a Swiss Vetterli last weekend, the bore was black with evidence of rifling. It cleaned up to shiney with minor imperfections.