I'm working on installing a new bathroom fan and when I pulled out the existing light switch to investigate wiring I found an older switch with looped black wiring. Our 90 year-old house has been partially updated from knob and tube wiring, but it looks like the bathroom fixtures still have old k&t wiring.

I've been searching all day through various discussion boards, and no one seems to be discussing this wiring solution/problem. What I have is two black wires, each of which has had a brief section of their insulation removed, and then looped around the screw on the switch. I assume that one loops to the lights and the other loops to the circuit box.

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Is it possible to update this to a double switch, one that goes to the old light fixture (with the existing black wires) and the other that goes up to the fan (with new NM wiring)?

I'd love to do this myself if it is safe and possible, but don't want to bite off more than I can chew...

Thanks in advance for any advice!