That's the real deal, beautiful original rifle.
Mismatched scope/mount to rifle (very common), but otherwise all correct.
Sum of the parts: Mk3 scope=$1500-$2000
original mount: $800-$1000
No4 T rifle: $1500-$1800
All prices US, based on on-line auctions and ebay.
Condition is everything, so that rifle might bring more. If the range/deflection drums are frozen, plan on an expensive repair.
Hope this helps.