Looks to me like the headstock laminations were sanded down for a repair. They often would lift on instruments of that era. Too bad they did not make a caul and clamp them back before glueing. They just sanded away the lams that were lifted. Not sure what the extra washers are doing under the switches?
Funny coincidence, I was digging through my box of cork-lined cauls yesterday looking for something to fit against a back brace in a Gibson LG-1, (that liittle drop-off near the end, where they
always come unstuck...) and there was the pair I made to glue-up the backstrap on 77-621 some years ago. Never know what you might need again. 😉
I think this bass must be from later in '77. Latter half of the year for sure. The washers are a puzzle... the switches look like the threads come too far through the body, so maybe the washers are there to take up some space? 🤷♂️ Replacements maybe. They look like the right switches though. Weird.