This is one of my favorites! It was made by C.T. Art Colortone for Boulder Dam Service Bureau. Made in 1941. The date is at the bottom 1B this is for 41. B is for the 40's. Cards were done like this in the 30's, letter A. 50's C. 60's D, mostly chromes instead of linen like this for the 60's.
There is a multi shot like this from Boulder Club & Las Vegas Club too. These are the only cards to the set made of this type for these 3 casinos. The Cinnabar had a multi card but was a different run. I don't have the others here so can't see who made Cinnabar.
I have the Frontier chips on ebay. Postcards just don't get any better than this. Note sign: Ladies Welcome.