Very Nice !!! My first thought was "is it micro-groove" or before then. As a gunsmith, I knew the change over was mid 50's but still don't know the exact date. I see them seldom in the shop for repairs and almost never see one traded in for a "new" gun. They hold their value well. A new one ( if Marlin ever makes anymore ) is over $600 retail.
I mowed grass all summer long in 1972 to earn enough to buy mine. ( Mom had to do 4473, still have it and it appears in as new condition ) It was right at <$100 with tax and a 4X Marlin (cheap) scope. The amazing thing is it will shoot one ragged hole at 25yds with anything from cheap promo loads to premium stuff.
Hope your's shoots as well !!
Thanks for posting pics,
Emri