Came home yesterday with an unfamiliar screwdriver.
It is 12" long, made of three parts: a wood handle, a receiver, and one interchangeable blade. The present blade is just under 5/8" wide and 1/8" thick.
The blade base is the shape of a wood auger bit and is held in the receiver by a spring that contacts one corner of the base of the bit.
It is clearly a quality tool of quality steel. Fit and finish are just right. I am likely to make another blade from a bit just for fun.
No maker mark--but a patent date: April 22, 1873.
Google image and DATAMP came up empty.
No pic, but any help will be appreciated.