Grayhill nice quality 16 button matrix keyboard with legend shown has an overall outer size of 2.7" x 3" and a raised inner keyboard of 2.5" x 2.7". When a key is pressed 2 pins out of the 8 pins at the top of keyboard are connected (See PDF). These are new old stock and the pins may have slight tarnish from age but are fine for connections. Originally retailed for over $30 each.
