I will check on your questions later this week. guitar is stored elsewhere right now so I only have pictures also. Pictures and memory.
The receipt is dated '71, no mention of production date.
I just did search on serial number and it makes no difference whether I put in J50 or J60. It says it was made in Kalamazoo or Nashville in 70, 71, or 72.
My main question still is about the receipt saying it's a J60. Is that possible?