Tom, yes that is the modern, or electronic version, which as I understand it, is virtually identical to my own units.

The Expo/Disc has been around for about 35-40 years and has applications in scientific photography as the light transmission is so well controlled it can and does get used for scientific photographic applications.

I know this from a photographer who did her Applied scientific photographic course from RMIT in Melbourne, became a forensic photographer, and is currently freelancing between various government and semi government scientific photographic assignments, that cannot be easily done, if at all, electronically.

You may find this quite interesting:-

http://expodisc.com/about/history.php

Mick.