That there is the Plus Fours Routefinder, the precursor to the roadbook and an interesting (if ultimately failed) example of pre-ID industrial design. Invented in the UK, the wrist-mounted device provided user-advanceable mapping information at a glance.
The central design difficulties are obvious: A separate scroll was required for each point-to-point trip, which allowed no deviation. It was also unidirectional, meaning you'd have to load a new scroll for the return journey.
The device was on display as part of the British Library's "Weird and Wonderful Inventions and Gadgets" exhibition several years ago. The Mail Online theorized that the device never saw mass uptake not because of its flaws, but because it was invented too early; that there were reportedly not enough motorists in the 1920s to support mass manufacture. I'm not sure if I buy that—you'd think that if the device had merit, one patient businessperson or another would've trotted it back out as the number of motorists rose.
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