I remembered the name of the ship: Bermuda Star. According to the below news item regarding an accident several years after our cruise, the ship belonged to Bermuda Star Cruise Lines. It may be that the same company "Atlantic Maritime" ran the casinos of the Princess Cruises ships at the time these 50 cent chips were used on the Princess ships (just speculation on my part mind you).
http://www.boston.com/news/daily/29/061290_oil2.htm