Here's what's in the file:
top: Myrtle
core: Cherry
back: Myrtle
neck: Maple and Purpleheart, 34 scale
fingerboard: Ebony with mother of pearl ovals
peghead veneers: Vermilion
originally built to: Musik Bertrum
birthday: July 27, 1977
I can't say I've ever seen a peghead joint quite as extreme as this one before. I asked mom, and she doesn't either. There is an usually large number of veneers on the back of the peghead as shown in your other photos. There isn't any notation in the file about it, but the information is scant, recorded on a samll 3x5 card at the time.
I'll add that I think this bass has been refinished. It's just not possible for the Maple neck to remain this color given the coatings we were using in 1977. Maybe a peghead repair and a refinish were done at the same time? The quality of the work looks nice from the photographs, and you're happy with it, and that's all that really matters.