Hi Jim,
We have the same card, and I have no idea whether the SC3772 is any kind of date code...sorry. (I only know the Curt-Teich code ).

As Phyllis said, the Hacienda opened in May of 1956. The next one to open was the Trop, in April of 1957. Since the Hacienda is claiming to be the strip's newest resort hotel, I'd guess that it falls in those dates.

Here's more Hacienda cards...






The bottom card was postmarked August 14, 1962, and was mailed from Las Vegas. The message reads:
Dear all,
Fantastic! But I'd say not a sweet fairy tale--rather on the crude side, for lack of a better word quickly. Nice trip & nice hotel and I know we'll enjoy it very much. It's most revealing and an experience. Keep well,
Love-Grandma S. Grandma K