This is a good clean Yankee ratchet / spiral screwdriver, clearly marked "YANKEE NO. 20-3 NORTH BROS. MFG. CO. PHILA. PA U.S.A. PAT. APR.16.95 - NOV.2.97 - SEPT.15.99 - OCT.9.00" near the selector switch. This is a rare model that was designed for spiral driving and ratcheting of screws (assembly line type production model), and was not design to remove screws. Note the selector switch is different from the No. 30A for example that is of similar size. The selector is position, left allows the spiral system to work in both dirctions (no ratchet), (note the single spiral on the spiral shaft in the picture where it is exposed, it has only a single spiral instead of a double like other standard models) and to the right is for driving screws. Comes with 3 different size hex Phillips tips and a Yankee to hex adapter that allows you to use the modern hex shank tips. We generally have other tips and hex and other adapters available for sale seperately for this Yankee brand model and other at this website. The chuck on this model accepts the largest size diameter shanks, 5/16" (T5631A Hex Adapter) and other tips should be ordered accordingly. This screwdriver has about 80% of the nickel plating is intact, most of the wear is near the selector switch, and about 95% stain finish intact on the handle, very nice. This type spiral driver is not spring loaded (no rapid return) in the spiral area drive area, works perfectly, as from the factory. 

This one is 16" long overall with no bit in place, fully extended, and uses the 5/16" (.312") diameter shank tips. Works Great! 
We also sell Yankee hex bit adapters for the smaller size of Yankee screwdriver separately at this website.