Working on K1801VM1 CPU core. It implements "Limited EIS" instruction set; silicon revision "G" also supports MUL opcode and has built-in timer.

Technical manual (reverse engineered from die shots) -- https://github.com/1801BM1/cpu11/raw/master/vm1/doc/1801vm1.pdf

This is a MS1201.01 SBC with that CPU, running modified PDP-11 BASIC from ROM, program loaded from paper tape:

[Linked Image from i.imgur.com]