@nprofile1q... @nprofile1q... @nprofile1q... those are generic physics engine, I doubt you can really tell them apart. Not sure what used Jolt but Bullet has been around for few decades already, some games definitely did.

Also, not to be super annoying, but don't forget that Source's physics aren't really the same Havok that everybody else use nowadays. Back in the day, Havok as company acquired another studio called Ipion and their physics engine that was used in Source. And that engine is a huge legacy, originated from 1990s.