stamped on the neck.
if you really really have to know I'd:
1) read about the bass mosrites on that forum
2) take your bass apart and take pictures of the inside pockets, butt of the neck, the head stock, electronics, pickups, everything pretty much.
3) make a thread there, with the history of the guitar, with links to the bands on wikipedia and talk about how wonderful the bass is. Be organized. Make a good enjoyable to read thread.
4A) ask if they can confirm its origin
4B) just make the thread and say you wanted to share your buy with them because you are so happy about it and wait for a Mr.Knowitall to stroll in and correct you. Then act surprised and be very thankful that Mr.KnowitAll blessed you with his mosrite dating internet skills.

