That looks really dusty. Hasn't been used for a while. That is the back panel and I can't make out what the modifications are. Google Minelabmods and it will take you to Ismaels website. Look under DIY and you will find instructions for doing the mods and which ones are suitable for which of the SD series detectors.
This is the FRONT panel of my SD2000.
The 2 RED dials are GAIN (sensitivity) controls for each of the 2 channels. BALANCE I is Channel 1 and BALANCE II is Channel 2, the 2 large black knobs.
The GB2+ toggle switch probably isn't necessary. I know I never used it.
The GAIN green dial is also not that important. I also did not use this.
This is the REAR panel of my SD2000.
The only mod you really need is the VCO. It is a 6 position switch with position 1 being off, then the next 4 positions are for 4 different frequencies, and the last position is for VCO only.
VCO is the only position I ever used. The toggle on the side is for the VCO and sets the frequency when in the VCO position to either HF or LF.
It's been so long since I used this detector that I can't remember what the green dial does.
Regards Axtyr.