Proofhouse.com has store brand chart
Marlin.
Marlin model 80
Most probably a rifle.
Store brand for Sears IIRC
Egunparts has a store brand table that might help
It was made by Marlin and is a pre-war version of the Model 80.
Marlin is about same as model 81
Blue Book of Gun Values
Was there a marlin 22 cal. bolt-action rifle made in 1920's?
When you say Air Rifle you are referring to a pellet rifle not a firearm. At present there are no 300 Cal air rifle being made.
Depending on condition, about $100. Your rifle is POSSIBLY a Stevens.
There are a lot of Sears Ranger rifles - what is the Ranger model number?