Can you post a scan? Hard to say for sure without a scan.
The Manchester sounds like the one listed in The Gaming Table (TGT) as from a Manchester, CA (card room, closed).
There was a Gold Country Casino (Indian) in Oroville, CA and a Gold Country Motor Inn in Elko, NV. The chip guides & TGT do not show Horse Head mold chips for either of these casinos.
Paul