The rifle is just like I bought it several years ago, except I replaced the Lyman Alaskan scope with another one of the same model and vintage. The barrel had been professionally drilled for a standard Redfield one-piece scope base and it had low rings for the 7/8 inch diameter scope. I do not know if the bottom of the scope base had been specially contoured for the Marlin barrel. However, the old Redfield base fits the top of the Marlin barrel like it was factory made for it. I do not plan to take it off just to find out.

(See pic added to original post.)