link: http://www.ebay.com/itm/272116893925 This one appears to be pretty early. The silkscreen is black instead of yellow, but it does have a copyright date of 1975, and no solder mask. It includes an early Intel 8214 Priority Interrupt Controller in white ceramic with gold lid and gold leads. I would guess it was assembled in mid-1976 by the IC date codes. You'll need one of these for MITS timesharing BASIC, or if you want to use interrupt-driven I/O devices. I've tested everything on this board except the 60 Hz timebase. That requires modifying your S-100 box to put unfiltered, unregulated 16 VAC on pin 55 of your motherboard, which I didn't want to do. I tested the interrupt controller by writing an initialization routine based off the example in the MITS 88-VI manual, and writing interrupt service routines to display the interrupt level on my IMSAI's programmed output register. Thanks, Jonathan