Looks to be late 70's. Here is an earlier post about my Crescents;

I have had a couple of older Crescents & they had a hard to find tire size. I contacted Schwalbe & they sent some to me. NO, NO bike shop will have that odd size. They are not even listed on Sheldons site.
Here is an old thread I made about a Crescent .
http://www.bikeforums.net/showthread...crescent+tires