We had a Fidelity Chess Challenger 7 when I was a kid.

I was a horrible chess player but painstakingly worked out a way to win as white, keeping a detailed log of my experiments in a notebook. The first couple moves were wildly out of book (because I didn't know book), and the computer with its limited Z80 processor always computed the same moves after that. Some googling [1] shows the board's Elo is 1300ish.

To illustrate the state of the art in 1979, the manual [2] explicitly calls out that it understands en passant and castling.

[1] https://www.spacious-mind.com/html/chess_challenger_7.html

[2] https://ia902902.us.archive.org/20/items/mame0.211manualsful...