The Watchismo blog has a great history of pre-quartz electrical watches, focusing on these wacky early Swiss watches with two huge external battery compartments:
This is the 1960 Landeron 4750, the first Swiss-electric movement. As you can see by the component diagram below, these were not simple watches like the inanimate battery powered Quartz of today. I'm featuring one of the more unique versions of this watch, the 'Montre à Couilles', as detailed in Pieter Doensen's book, built as a demonstration model with two externally cased battery compartments.
See also:
History of slide-rule wristwatches
Early days of plastic watches
Mechanical "LED watch" from 1970
History of calculator watches
Steampunk watch
Belt-drive watch
Watch guts of great beauty
All-plastic watch movement from the 70s
Awesome, impractical, expensive watch
