...band razors.
Considered by many to be the red-headed stepchild (no offense to the red-headed stepchildren out there) of the razor world, band razors use a spool of thin steel encased in a removable cartridge with one edge sharpened and exposed. Each length of sharpened edge can be advanced, once its reached its useful life, by turning a lever on the back side of the razor's head.
A counter, much like that on a film camera, keeps track of the number of edges used. Used edges are stored on a take-up spool, so the user never touches the blade.
Gillette introduced the Techmatic in 1965, and supplied Gemini and Apollo astronauts with them for use during space missions, with varying degrees of success.
There are several other, older versions of the band razor, but would probably rarely be seen. The Gillette and Schick can still be found on online auction sites at fair prices.
Band razors have a very low level of popularity among wet-shavers, supposedly due to the razor's inability to maintain a flat edge. I recently received a NOS Techmatic, along with three NOS cartridges, and put this theory to test. My results? A new edge gave me a shave on par with a single-edge injector razor. In fact, it handled my trouble spots *nearly* as well as a double-edge razor. Will I make it my daily driver? No, but it will come in handy for times I'm pressed for time and need a quick, smooth shave.