Simon,
My apologies if I'm a bit slow here or missed something, but in all of this Lee Enfield fiasco in its history of numbering anomalies and weird locations for such numbers, the one cohesive thing you could bet your shirt tails on was invariably the wrist number matching the scope, because afterall that is what it was all about............a perfect match.
Clearly this would have been right at the time, and lots of changes could have varied that in the meantime. Was the AR-1018 stamped on the wrist band evident? if it was , one has to assume the two were parted somewhere in history for whatever reason.
Could it be as simple as, one of the rifles that went to the USAand parted company there with its scope on sale to civvy RFD's, which a number did?