Interestingly, I remember that by friends 335 serial stamp on the ‘show model’ 335 was wonky. It described the age to be 1967. This supports your idea that the serial was placed before final assembly. I do remember reading the letter from Gibson that stated that the neck was destined for a diffferent guitar, but ended up on his, again, a ‘show model’ 335.
All that being said, I have a Melody Maker from that era and the serial is almost impossible to accurately verify year, model, etc.
I feel that Gibson was interchanging necks to put together final instruments between 1967-1971ish, and it is possible that this original thread post is a victim of a great deal of uncertainty about how necks got matched to final builds. That is all.
As others have chimed, I really dig the crown inlay on the second run of LP guitars leading into the eventual Norlin era, and also wish we had more crown inlay head stocks offered on contemporary model LP’s, as they look really cool. Remember several GOTM models that featured the crown?
As we now know, the crown/flower pot inlay with binding has made several appearances on LP headstocks. I have one on my '04 Standard LE. I think it's very classy, and distinguishes it from all others..