I think this is it, the 500/4 model.
I don't know why it says "solid bass guitar" when obviously it's a hollow body. Yours seems to have had an extra knob added. Here's the site I found it on. You can search through the bass section, but there are no other models that look like the 500/4 having 4 knobs. Also, the 500/4 is the only dual cutaway hollow body bass with the same horn size as yours.The other dual cutaway models have much shorter horns.
Here's the official Hofner site bass page.Same thing here. The 500/4 is the only dual cutaway hollow body shown having the same size horns as yours.