I stumbled upon an image of a calculator the other day, and I really liked it so decided to replicate it in HTML/CSS.
This is the Abatron 803 from 1976: https://www.calculator.org/calculators/Abatron_803.html
The original image I stumbled upon (which I thought was a real calculator too) and inspired my design by turned out to be a photoshop creation by https://dribbble.com/shots/499001-Abatron-Calculator-Buttons. That design was an interpretation of a real calculator from 1975, called the Abatron 803.
However, I have since edited my design to reflect the design of the real Abatron 803.