Benjamin 312

I have a Benjamin 312, .22 in the original Abercrombie & Fitch box with the owner's manual, schematic, screw driver and partial tin of Diablo pellets that came with it. It's in excellent shape. No ser.#, which I understand means it was mfg'd. before 1957. Never fired it and don't think it holds air. Anyone have an idea what this may be worth?

Thanks