I don't know anything, but that looks like cocobolo to me.

I too have a Series I with the added master volume.    But I believe it was added at the factory when the bass was made in 1975.    All of the date codes match.   Having a master volume is really handy.    I rarely keep my pickups at the same volume.   I find the master works great, that way I don't have to bring the channels down separately.

Michael

Beautiful top; congrats!  I'm guessing Coco Bolo as well.