Testing a Rusty Regula 25 Cuckoo Movement

I recently purchased a rusty cuckoo clock movement on eBay - which was advertised as being rusty, so all's well. As a first step toward repair, I test whether and how well the movement runs.
It works surprisingly well for being so rusty!

[@tahoe829]

I watched a video that said that cuckoo clock movements have mainsprings that drive the first wheel and gear train but i dont see any mainspring on the strike mechanism at all. Purely gravity and mass driven is that correct for a 1 day regula movement?

[@BradfordNeedham]

I have seen some cuckoo clocks that do have springs, and their weights are simply decorative (the chains don't move). Most Regula cuckoo movements I've seen don't have mainsprings. As you say, they're driven entirely by gravity & the mass of the pine-cone-shaped weights.