Cat Man wrote on May 23^rd, 2017 at 9:22pm:

Oly O, You have a rifle that was arsenal drilled to accept the Norwegian Target or Sniper sight. What does the receiver ring say on the left? Anything stamped above the serial number? The M25 sniper rifles had a fully adjustable aperture rear sight that is mounted with three screws. Target shooters also had these sights installed.

GREAT information and THANKS.  It certainly would have been nice for the M25 thing to be true, but no, there is no M25 data or stamps on the left receiver. 

I'd come to the same conclusion regarding the sight just by looking at the bolt pattern, but it's fantastic to hear a confirmation.  I can look for one now!  Thanks a million, and if there's anything else I should know I'm all ears and very grateful.  The rifle itself is in fine condition with a great bore, so I do very much want to get it back on the range in top shape.

Best,
Oly