That’s kind of a generic large-ish mixer (well, large compared to a hand-held kitchen type mixer). You could mix other stuff as well, though there isn’t all that much stuff that you need to mix in batches big enough to require a two-person mixer.
If it’s close to construction, it’s almost certainly supposed to be a mortar mixer. They were commonly used when building castles and churches. There should be one person on each end of the beam pushing it around, and possibly a third person throwing stuff into the big bowl. It wouldn’t be left unattended like that, especially with freshly mixed mortar still in it. They only have so much time to get the mortar out of there and onto the building before it sets up.
The thing is, these types of mortar mixers were temporary. They would usually dig a pit next to the construction site, then build the wooden bits and mix up the mortar (in very large batches because they were making something big), and then when they were done they’d fill in the pit and move on. The one in your screen capture looks like it has a stone base, which wouldn’t typically be used.
See this picture, for example:
A large mixer like that with a permanent stone base would be more common in something like a tile manufacturer, who used the mixer to mix up clay which would then be formed into tiles and fired in a nearby kiln. This would be a permanent setup and wouldn’t be next to a construction site.
Another design for mortar mixers is to replace that main beam (which is obviously designed to be pushed by two people, one on each side) with a pole or beam attached to a horse or some other beast of burden.
A similar device was used to mill grain, but instead of having a big bowl and stirring rods, you’d have round stones used to mill the grain attached to the crossbar. But it’s the same basic idea. You have a large cross-beam that can be pushed by two people (one on each side), or a slightly different design with a beam attached to a horse or some other beast.
I went poking around on google and found a youtube video showing some researchers experimenting with this type of mixer: