Looks like a double SG on the left and a double headless Cort or similar on the right, whilst in the middle you correctly spotted a Riccy copy and the volume & control pots are wrong and also looks like a split P Bass type PUP up front too. Geddy Lee & Alex Lifeson from Canadian Band RUSH used double neckers quite a bit and I also found an example of a SG Bass/Guitar double.
Apologies Andy, did not mean to be so indulgent with the thread hijack and beg your forgiveness.
Edit, love how yours is coming along and can't wait to hear the sweet sounds it should produce.