On the multi-property mustard One Club cards 42nd issue it lists Circus Circus - Las Vegas and Slots A Fun on the front but a second variation of that card was just discovered that has a slightly different reverse.

Below is a scan of the common front, then a scan of the back of the originally listed card where the bottom line of text on the back with the phone numbers ends aligned with the right end of the paragraph of text above. And finally a scan of the back of the newly found card where the bottom line of text on the back ends further left from the end of the paragraph above. Once you see both cards side by side the difference in the reverse text is pretty clear.