Any Info about Korean Toby pro V???

I recently got my hands on a Korean Toby Pro V and I'm trying to learn more about it. I've learned that Gibson bought Tobias in 1990 and that the Toby's were built in the Korean Epiphone factory. I checked the serial number on the official Gibson Epiphone site and its telling me it was built in Dec 85 which must be a mistake.
I have read that someone in the factory was taking odd bits home, finishing them and adding random serial numbers so that's my first concern although this is a through neck so less likely to be the case.
I know the original owner who I believe purchased it new in 97 but I can't get any info from him because he borrowed the money (from me) to buy an original Tobias and had been passing it off as such since. It's taken a beating but I am enjoying this bass and thinking about possibly making some upgrades. Advice would be most welcome. Serial number 5120316.