See <http://www.classiccmp.org/hp/avl1/hp-test.jpg>. It's marked "FDB Test Board" and it's PN 10921-60009. You can't see it in the photo but the LEDs are labled 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, COMD, COMC. I found this in a box of HP 1000 parts so I suspect it for the 1000 or one of it's peripherals. Joe