This looks like one of those projects that started out as a glimmer ... that leads to homebrew neon seven-segment displays on a calculator with relay logic. It’s a little thin on documentation ...

Renovating or considering a home improvement project? See how much it could cost, based on what other homeowners paid across the nation. The calculator includes national data. Keep in mind that ...

[Eric] and the late [Richard Ottosen] have been incrementally developing various DIY calculators — this paper from the 2005 HHC conference is an excellent overview of the early project.