Scope a newly manufactored Double, a 9.3??
Of course!! It would help with long range shots--

My Merkel 500 NE? Sure, Maybe with an aimpoint red dot 2x power with unlimited eye relief but not much else.

Scope an English classic??--Dunno about that. You would have a scope/mounts that was not period specific for the gun and the mounts/scope might seem out of place.You might even decrease the $$resale value substantially by scoping.

Bottom line -it obviously depends on the gun!!