Hi Hasse,
Glad to hear that nice old bass has found a happy home with you. It really makes us all happy hear to learn that you are finding yourself playing more - as beautiful as these creatures are, they are meant to be played and enjoyed.
I'm sorry, but the file for you bass is currently missing, unless someone else started to field your request and already pulled it (we can hope!). From the picture, I will guess the top to be some sort of Rosewood, although it's so dark, it's really hard to tell.
I can tell you it was finished somewhere between May 1 and May 8 1977 by the adjacent serial numbers.
When you get a chance, please take some more pictures and post them in the Series I section of the Showcase. If you can take a photo of the inside of the electronics cavity then we can tell you more about the switch. I bet it was for stereo/mono for the 1/4 jack.
Even though the picture is dark, I'll bet both of those pickups are replaced. Are the dials that were replaced the center two trimpots accessed through the backplate? Or are there holes on the front without controls?
Did you get the power supply and 5-pin cable with the bass?
Did you know you were going to have to answer so many questions?