With all due respect to BMbikerider, I must disagree with his dating estimate.
Kodachrome rolls of 18 exposures were introduced at the very beginning of the 35mm Kodachrome lifecycle, around 1936-1937.
You have in your hands, Rich, a glorious piece of photographic history.
Here is what the outside box looked like.
I hope someday that you will find an original box and complete the package.
Best of luck.
I've got several Kodachrome packs dating back to 1937 but they're still sealed boxes and so I suppose I'll never get to see what's inside!