Definitely a flaring tool for creating flared ends for copper or soft metal tubing. It was a tool they were still teaching us to use in automotive classes in the late 1980s.

We learned how to make single layer flares and double layer flares with those.

Learned all of it and then never needed to use one ever.

If anyone wants to learn how it is done here’s a good vid on the subject: https://youtu.be/_Tm6N5l69_c

That makes sense. It didn't come with the other part, but there's a bunch at a thrift store nearby, which must have been where I've seen it before.

Ohhhhhhhhhhhhhh!! (Seriously. That was a revelation for me)

This. But most pullers I've seen have unfixed jaws to accommodate a range of bearings.