Conchess Plymate

Conchess Plymate is a series of chess programs by Ulf Rathsman and Lars Hjörth written in Assembly to run on 6502 based dedicated chess computers with up to 8 MHz. Plymate was marketed as cartridge for Conchess computers, and was further incorporated inside the Mephisto MM II by Hegener & Glaser. Plymate played four ICGA world computer chess tournaments, the WMCCC 1985, WCCC 1986, the WMCCC 1987 and the commercial group of the WMCCC 1988.

This was made in Sweden but the pages online about it are in German.
https://www.chessprogramming.org/Plymate For history
https://de.wikipedia.org/wiki/Conchess (No English version)