Good luck on finding this postcard...it's a toughie!
I have this one, as my mom thought it was funny and bought it many years ago when we lived in Vegas.
Several years ago my mother gave me all the encyclopedias that I had as a child. I went through the books before handing them off to Goodwill....thank heavens, as I found this post card and all sorts of Vegas goodies tucked between the pages.
Last time I saw one of these on Ebay (about a year ago)...hold onto yer shorts....it sold for a little over $100.
I haven't kept track of these since that auction, so hopefully that was just a high frenzy bidding war.
Good luck.