Congrats GAD!
I assume that is a Custom Shop model and thin like the '60's SF4's. Technically a SF5 would have block fret markers and a deeper body.
The little mini toggle is a 3-position switch. In the "Up" position (i.e., pulled towards the bass boute) the 3-way neck, neck+bridge, bridge is activated. With the little toggle in the middle position the middle pickup is added to the N, N+B, B combination. In the "Down" position only the middle pickup is activated. The knob controls are Volume for each pickup and Master Treble control.
Very cool guitar with good tone selection and variety.
PS...The middle pickup is counter wound so you can get the airy single coil tone when blended with neck or bridge.