Still working on the pics, but I was able to identify that screwdriver. You folks are good luck! Turns out, it's a Dunlap machinist screwdriver. There's one for sale at goantiques that looks just like mine, and a couple on eBay that are the same manufacture but different sizes. The lettering is so faded it can't be deciphered, but that's the one. I found it because I was surfing screwdriver sites; (bought a Yankee screwdriver at an auction today that's unlike any of my others), and there it was! The new screwdriver is clearly a knockoff. It's a size 30, but completely unmarked. The locking collar is marked stop <- -> move. It's all nickel plated and some of the plate is off. The handle is red plastic with a yellow ring near the shaft. It seems to work well, but came without a tip, so I ordered an adapter from Lee Valley for it.
