Mattel's Computer Gin (1979, LCD, 9 Volt, Model# 1669)
U. S. Patent # 4,314,336
& 4,380,334
U. S. Design Patent # D266,935
(patent on the look of the game housing)
Invented by: William Bernstein, Robert Del Principe (1st patent), Michael Minkoff
and Raymond Kaestner (2nd patent)
View Manual
Apparently only a fair rendition of the card game. There are things you can do in real Gin that aren't implemented in this handheld game. Mattel had designed a Computer Gin II to come out the following year that played Gin more or less perfectly, but it was never released. (Only one prototype is known to exist).
Do I have this? Yes, boxed (bottom pic is mine.)