That's a Singer 301. They were made around 1953. That one looks like its had a hard life. They are a great machine when they are cleaned up. Not only is it a great machine in a cabinet, there is a lever that you push and the machine lifts right out so that you can take it to a class or whatever. Singer 301's are considered the big sister to the Featherweight. They are a lightweight full sized machine with a handle on top for carrying. They take slant shank attachements.
If it were me I would offer them less for the machine.
Good Luck!
Colleen