Here's my explanation of the 1992 and 1997 dates --
Pre-Harrah's, this mid-strip property was Holiday Casino (with a Holiday Inn hotel attached). It closed in 1992 when it became Harrah's (see Holiday close date of 1992 in ChipGuide, which coincides with Harrah's open date of 1992.

At first Harrah's kept the riverboat theme (see pics of earlier post cards on ChipGuide). Then, 5 years later, in 1997, they changed to a Mardi Gras theme, complete with re-doing the facade with the showgirl mural by Henry Conversano. The 1997 date was simply the grand opening of the new facade and theme. Looks like they had a big party to kick off the new look, and the lucite item commemorated it.

As an aside, Harrah's was opening other locations, and in 1995 they opened Harrah's-New Orleans, also with a Mardi Gras decorative theme. So they had some experience with that look, and evidently liked it, because 2 years later, in 1997, they went with a similar look when they updated Harrah's Las Vegas.

Does that all make sense? That's how I explain both the 1992 and the 1997 dates.