I found this on the Ebay Vintage Clothing Discussion Board. It is a way to Date RN Numbers. I've tried it out it seems to be correct or at least very close. Try it out and let me know what you think. To figure the RN#: take the RN and subtract 13670; divide that number by 2189 (average rn #'s issued per year); add that number to 1959 (when rn #'s started) and that will give you the a/ issue date. So, 76256 - 13670 = 62586 divided by 2189 = 28.59 or 29 = 1959 = 1988. So a/ rn date is 1988.