Whilst looking at fuses in the cubby hole behind driver I noticed
A small box about 2 inches by half an inch, it has a knob like a
Volume control which says 9db minus to 9 db plus, it also has a small
Button. What the hell is it, any one got an idea...

someone probably installed an aftermarket sub and put the amp for it in that location.

It's a bit small for an amp

Follow.the.wires they will lead to the amp or where it resided. It's a gain switch. The amp, if still there, will probably be in the trunk or behind the passenger kick panel.

perhaps I should follow the yellow brick road......

Can you picture it..?, or forward the part # if it has..!

;ZAYED;