So it sat around for another year until I got the wild idea to ask the
NeoNixie list for help in designing the case. I ended up working with John
Smout of England, who does 3D product design for a living. He was able to
come up with some nice drawings of what I was thinking of - a square case
with the battery to one side of the two tubes, a rectangular crystal, and
screws in back holding the case together. It was looking sort of like a
watch, but something wasn’t quite right.
Then, while I was walking the dog one night, I thought about making one side of the case round instead of square, like the old Hamilton Electric watches from the late fifties. I soon realized that I could make both sides round, and it didn’t take long until the whole case was round.
I realized then that if the watch was round, the cover could be threaded on instead of using screws. The designer’s dream - no screwdriver needed! The water seal would be an o-ring around the outside of the case. The crystal became round, so it was easier to purchase. (It ended up being easier and lower cost than I ever imagined.)
As I pondered the perplexing problem of what to do with the back of the watch, I decided to study the mechanical watches I had lying around. They all seemed to have the same general design - a big turning with the strap lugs formed by punching out the material between them and from the sides of the watch. I had to approach it a bit differently, since I had an o-ring seal to get in the way of milling away material from the front. So I had the material milled from the rear. But I used the idea of turning the strap lugs, which is what gives it that watch-like look.