Look on your fender tag, my 70' has the estimated build date on the last line near the right. It might be on the second line up. It will be a three digit code. 110 will be Jan 10th.so 1 thru 9 is Jan to Sept. A is oct, B is November,etc. the next two numbers are the date of the month. That date is approximate, It could have been a few days later. That's all we get.