Developed by Al Schneider in 1960 and published in Genii 1970 November (and republished in Genii 2000 February ). It's a variation of "Sympathetic Coins" by Yank Hoe, published in The Art of Magic (Hilliard/Downs, 1909). He originally called it "Coins-n-Cards". Karrell Fox suggested "Al-ternating Coins", but being a physics major in college at the time, he decided on a math term for a rectangular array of numbers, Matrix before publishing in Genii.
Schneider was at one time collecting variations for a book titled "The Methods of Matrix".