I found my old Nintendo Game & Watch Donkey Kong (DK-52) pocket game the other week. Some 30 years ago I took it apart and never bothered to put it back together - but all the parts where in one place. Thanks to detailed instructions over at Damn Technology I managed to put it back together correctly. And it works! Sound and all!
On a related note, I would like to extend a big Thank You to all those who worked to standardize battery sizes. Thirty years on and I can still walk into any store and buy a pair of LR44 batteries suitable for this device.