Thanks. It does look likely it has a hydraulic chamber. But there are no moving parts on this. And under the red cap on top there are a few ball bearings stacked in a threaded hole. Don't know if that helps in identifying
I'm guessing the moving/rotating part would be the long sleeve/nut, to wind the leadscrew in and out. That's only a guess though, as I've never played around with a hydraulic vice as yet.