Mark,
The three chips were sponsored by the Las Vegas Convention and Visitors Authority and Laughlin Visitors Bureau. They were give-aways to the first 5,000 people thru the gate on those nights. The dates, other than the first one which was opening night, 1998, have no significance. I have traders and will trade for any cruise ship chips I need. Last year Gila River Casinos offered a token as a give-away. I had to ask a favor of a gate attendant to get one because I was not at the game the night these were given away. I'll post a scan of it following this.