The original chip inside the Sinclair Scientific Calculator was reverse engineered by Ken Shirriff, its 320 instruction program extracted and an online emulator written. There’s a video, below and the project’s homepage on Hackaday.io describes it all perfectly:

If you can’t find yours or you never had one, now you can build your own using - what else - an Arduino thanks to. We’ve talked about the Sinclair scientific calculator before many times, and for some of us it was our first scientific calculator.