It's a Tune Bass Maniac. They first were released in the mid 80s and aspects of the design were quickly used by Ibanez,Nanyo SGC and Washburn.
There's 2 companies using the Tune name. One is still in Japan and holds the rights there.The other is in Korea and has worldwide rights.
Thanks to Tune super thin necks are quite common and the Bass Maniac is still in production.I saw your other post and don't think the number is a serial one.
Here's links to both companies
Tune bass guitar official website
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And congratulations on having a fine bass.I was 30 years waiting before I got mine