Hi Allan,
A day of searching antique shops turned up some great old Nevada matchbooks . As always, I looked for all of them in The Gaming Table, even if it didn't seem likely that I'd find them.

To my surprise, I found a listing for "O.T.'s Drive In"!!! All it says, however, is Las Vegas, NV USA closed: yes

Here's the full address, assuming it's the same one:
O.T.'s Drive In
1731 North Main St.
No. Las Vegas, Nev.
phone 1815-M

In the same group of matchbooks was one from the •Playland Bar & Arcade (1943-1945), and one from the •Saddle Club (1944-1945), so I suspect that O.T.'s was circa 1944.

None of the others seem to be casino related...but I'll list them here, in case you're interested:
•The Sportsman's, Boulder Hwy, Dogpatch, Nevada
•Mina Mansion, 309 Tonopah, Hwy. 95, 1/2 mi. N. of Twin Lakes
•Carson Beauty Salon, 417 Carson, Las Vegas, Nevada, phone 1988
•Troy's Club, 2506 E. Fremont, Las Vegas, Nevada, Phone 4085-M
•Maggie's Pantry, South on La. Hiway 91, Las Vegas, Nevada, telephone 3252
•The Malt Shop, 5th & Carson, Las Vegas, Nevada
•Sill's Drive In Restaurant, Fifth & Charleston, Las Vegas, Nevada
•Corey's Cafe, Fourth and Fremont St., Las Vegas Nev.
•Ethel's Liquor Store, 28 Fremont, Las Vegas, Nevada, Phone 117
•Elko Auto Court, U.S. Highway40, East end of Elko, Nevada
•Boulder Dam Hotel, Boulder City, Nevada