Just checked my collection and I found the P1 prefix that you can add to the list.

I've been calling Boyd corporate marketing for weeks with no answer, no return call, etc. If someone else wants to try, the corporate phone# is 702-792-7200

Once we track down the prefixes I can add them in the Slot Card Guide appendix to go with all the other player# prefixes that I've tracked down.... Main Street/Fremont/California; Casino Magic, Coast, Golden Nugget (Landry), Harrah's/Caesars, Lady Luck, Terribles, Trump One Club as well as the barcode# prefixes for all Montana cards.