The neck plate says Made in Japan, as for the neck construction, I reckon its prolly a cheapo, the fretboard almost looks like plastic or urethane based. I dont know what you mean by 3 pieces. Is that down the length of the neck or accross the face of it as in like you would attach boards together to make a table. It looks like one bit though. The nut doesnt look to be original either, it has what looks like match sticks underneath for support lol. Still sounds luscious though.
A 3 piece neck has the joins running top to bottom. It would be fairly obvious if it is a 3 piece as it would have cross sawn wood in in there.
Where abouts is the MIJ stamp? 3 thirds of the way down (i.e. nearer the bottom)? The pics you've supplied rely aren't good enough to help in IDing this. I suspect some of the hardware has been changed (like the scratchplate). To find out more you'll have to start stripping the bass to look for clues. The pickups may be stamped to indicate the date, stamps on the neck, and it may have holes where the thumbrest was originally located below the strings.
Do the pickups have rounded ends, and what does the bridge look like?
Lots more clear pics please!
Edit to add: Without the name on the bass you'll never find the brand, but we might be able to ID the manufacturer.