I have my grandfather’s J-45 and have found no way of dating it, as of yet. I would say it’s a 60’s from the block logo. There is a metal plate embossed with GIBSON on the back of the headstock where the SN would normally be, and a 2 stamped just above, indicating it’s a second. No SN on neck block. No sticker inside, just J-45 ADJ BRIDGE stamped on back inside wall Any assistance is greatly appreciated.