Here's a photo of my model 36..SN 8J66xx.. I think this sequence was only used for 1968,prior to the J series.
woftrax
woftrax, it can't be 1968, back then there were no letters in the serial numbers. How many digits after the 8J? Let us know, but I suspect your gun is from the "floating J " period of 1971-1972.