"boulderdash" sells these on eBay. His eBay store is aaascrapdogsunlimited. This is what he has to say about the operation. "This board is set to boot to JIFFYDOS by default to boot to the c= kernal hold down the RESTORE key when booting the commodore 64."
I sell them on ebay the board has a simple IC circuit that will switch between jiffydos and the c= kernal when you hold down the restore key on a vic-20 or c64 or SX-64 or the caps lock on a 128 128d 128dcr or press the reset switch on a plus4 or c16 that way you do not need to drill a hole in your case ken.