I am helping a friend value some rifles he inherited. I need help with a marlin.

It has not markings. It is a rifle with a long round barrel. It has a pistol grip stock and a bulbous for end. The magazine tube is shorter than the barrel. It is in a large caliber.

The action is the closed face type similar to a 1894, not like the current 336's.

Where do I look to figure out what this is?

Thanks In advance

jerry