The Commodore 500E calculator (above) and the nixie tubes that make up the display (below)
The Old Calculator Web Museum is a treasure trove of images, specs, advertisements, and articles about the calculators of days gone by. Many of the calculator profile pages include photos of the insides. My favorite area is the retro ad archive, though.
The museum is looking to flesh out its collection: there is an extensive “wanted” list.
Aha. I found a 500E discarded by the chemistry department at RPI c.1997 — or something similar; I definitely remember the general shape, size and nixie tubes, but would’ve noted a Commodore logo. “I could do something cool with this, eventually,” I enthused, and lugged it back to the dorm, to lurk beneath my bed; but its bulk and weight (solid steel chassis, it felt like) dissuaded me from carting it home at the end of the semester.