Many of the late serial number rifles in the 600-700 range were assembled from parts swapped directly to Charnwood Ordnance by Enfield when the Pattern Room was moved from Enfield to Nottingham. They are easy to distinguish as they have no serial numbers on the bolts but are otherwise assembled from new condition original parts. There were Savage Mk.1/3 receivers used including the last documented one produced, serial number 767 so it's perfectly feasible that some Long Branch Mk.1/3 receivers were also used.