on the Internet...

Gemaco Inc. was formerly known as the George C. Matteson Company. In 1965 Matteson launched a new venture as a supplier of playing cards to the gaming and promotional products markets. The company prospered and the GEMACO (pronounced gemaico) brand became a highly respected and significant supplier of casino cards. In 1992, Matteson and his associates sold the company. He served as chairman emeritus until his retirement in 1994, and was elected to the industry hall of fame in 2002. George C. Matteson passed away on May 16, 2011.

I'm leaning towards generic! Of course Reggie could also be correct and Diamond Mountain Casino may have been using generic GEMACO decks.

Thanks,

Jim