Hee hee hee....good one Jack.
geniefunk,
One or two years prior to selling to EB in March 1984, Music Man was having trouble with their Bass necks (truss rods). My toss is that your Bass was one such instrument and that the neck was replaced by EB after the take over....that would explain the Pre EB serial# and the headstock sporting the EB logo, which, in turn, additionally points to your serial being an 83 or early 84 number. On the other hand, it's possible your number could be one of those rogue serials I was taking about and that your Bass is earlier than 83/84.
The only sure way you are going to find out is to take the neck off and inspect the the date at the heel and the date in the body pocket. That should only take about 5 or 10 minutes. If you're uncomfortable about doing this, a luthier should be able to do it for you while you waite.
Cheers.
P.S. Just an after thought....are the strings top-loaded or do they run through the body???