A quick Google had a couple of sites showing this as using a Venus 2790. But as far as I know, Valjoux gave its own names to the Venus movements it adapted and carried on using after it took them over Venus in 1967 (e.g. the Venus 188 becoming the Valjoux 7730).

Now I'm not sure of what internal politics govern whether a movement gets a Valjoux or an ETA name, but there is an ETA 2790, so I would guess that this is what is actually used in the Solunar (the later watch gets this shorter name).