Back before hobbyists enjoyed large enough discretionary incomes to afford a variety of single-purpose tools, several manufacturers offered these at attachments for your power drill or an interchangeable motor. This is a planer produced by Millers Falls. It's interesting because, unlike portable planers today, this one is more like a stationary jointer: it came equipped with a fence which could be adjusted for beveling, as well as a spring-loaded guard over the spiral cutting head. Rather than being designed to use with a power drill, it seems that this tool would have had its own removable motor, which could be used in other similar attachments made by this manufacturer. (I'd be grateful for any information on what this motor looks like, and how it attached to the tool.)
Update July 7, 2015: Yesterday I picked up a copy of John G. Shea's book, Woodworking for Everybody (Van Nostrand Reinhold Co., 1944, Fourth Edition 1970) with the photo below:
It turns out it was designed for use with an electric drill after all! I still don't understand how it was attached, because if it's clamped to the chuck the whole tool will rotate!
Porter-Cable had their own version:
|Manual of Home Repairs, Remodeling and Maintenance. Grosset & Dunlap, 1969.|
|Popular Science, December 1957|