slavin:

via Greenfield:

“This fantastic contraption, called the ‘Routefinder’, showed 1920s drivers in the UK the roads they were travelling down, gave them the mileage covered and told them to stop when they came at journey’s end.

The technology – a curious cross between the space age and the stone age – consisted of a little map scroll inside a watch, to be ‘scrolled’ (hence the word) as the driver moved along on the map. A multitude of scrolls could be fitted in the watch to suit the particular trip the driver fancied taking.”

(via 314 - Watch the Road: World’s Earliest SatNav | Strange Maps | Big Think)