Around 1990 I picked up an old Sharp calculator from a flea market because it was only a couple of bucks and had 16 nixies. I believe it was this Sharp calculator model from 1969. I say I believe because at some point when I moved I threw away the case and keyboard, no perceived utility. But that the CS-361 had magnetic core memory fits with the main board I still have.

Well it's a pity I don't have the complete machine because it could have been of interest to a museum. I'm fascinated that it used core memory. I thought it was for microcode storage, but the web page says it was for registers. The microcode probably consists of diode logic. You can also see it has germanium transistors in metal cans and plastic silicon transistors.

No, I'm not going to try to reverse engineer the logic. Just thought I'd publish a picture of the main circuit board before I put the nixies to other uses.