Oobject has a list of the “top 15 calculator watches“. I’m not sure what critieria they used to pick them, but you can vote them up and down the short list. They’re drawing most of the info from the fantastic Vintage Calculator Web Museum and LEDWATCHES.NET.

Here’s the 1975 Pulsar Module 1, probably the first ever calculator watch:

A heck of a thing. There’s also a gold version. If Module 1 had two dissimilar children, and those children had families, then a couple of generations later those families might look like my own two watches…

… the Casio CA53W-1…

… and the LIP Diode recreation. Thank you pulsar.