Signetics 2650 is an obscure CPU that was the victem of corporate delays. Its quite different to Z80 and 6502, but had 7 registers and an integral stack so coudl run without any memory.

Anyhow the signetics 2650 advert showed a cool dev board and I wondered if we could get a Tiny BASIC running for it

Yes we can! (probably) See Github Page for source.

To try it in a browser with a showcase demo populated in RAM
https://vincbr900.github.io/2650-Tiny-BASIC/

Next step is to actually build hardware assuming we can find a working CPU.