Thanks to Glenn’s website covering the history of Gillette’s adjustable razors, I found a very important number… the number is one million, five hundred and ninety nine thousand, seven hundred and ninety three. As in US patent number 1 599 793, that is.
To quote from the patent description, it
…relates particularly to an index’adjusting device for use in connection with safety razors of the Gillette type wherein a flexible and elastic blade is provided with cutting edges that are adjustable toward and from the guard member of the razor
In short, it’s about how to make an adjustable razor adjustable.
As can be seen from the image, everything interesting is happening in the head or right below it. Adjusting the dial 16 makes the top cap move up and down in relation to the base plate, while the base plate stays fixed in relationship to the handle. In order to remove or insert a blade, the shaver would turn the dial around and around to unscrew the cap. In other words, this very early version of the Gillette Adjustable works much the same way a Merkur Progress does – although without the central bar the Progress have.
I don’t think Gillette ever manufactured – apart from prototypes – this razor, although it must be pointed out that the method of adjusting this razor bears a lot of resemblance to how Gillette suggested one could “adjust” an Old type razor back when it was first offered:
If a close shave is desired, turn the end of the handle back a little and the edges of the blade will lift slightly from the guard thus permitting closer contact with the face. A moments practice will show the proper adjustment.
The patent is expired, and thus anyone can make a razor like this today; however bear in mind that other aspects of a good adjustable may still be covered by patents. It would still be interesting if a machinist decided to have a go though, so we could compare how far this version is from the other adjustable safety razors.
/Update: I originally believed this was an early Gillette patent, but discussion and research by the members of the Shave Nook showed that this patent was never assigned to Gillette.