Jazz bass controls

[Daverigbyturf]

Hi there,

just started with the bass and borrowing a jazz bass.
The control plate has 4 controls. The 2 first I believe are volume for neck/bridge pickups. Then I have concentric/stacked plus a smaller last one.
Any tips on what it is?

 

[RattleSnack]

I would guess that's bass guitar with active preamp, so check for battery compartment on the back of body.
If that's true, than controls are probably: master volume, balance, treble and bass stacked (treble on top), and mids control.