Of course, "The Watch of the Future" was only true for a relatively short time; technology had moved on with the likes of the Bulova Accutron and the early marketing disasters of the 500 all contributed to the final electrics being manufactured in 1969.

As far as I'm aware, there was never a tuning fork watch with Hamilton on the dial, but Hamilton did join the growing number of other watch manufacturers using the highly successful electronic ESA Dynotron movements, and like many other watch companies, adopted their own calibre numbering system for these ESA movements:

• Hamilton Cal. 683 = ESA 9154
• Hamilton Cal. 702 = ESA 9158