What is this strange circular thing ?

[rustyric]

Wow I am impressed - A pipe clamp ! Makes sense now, a third hand for when your sweating a joint !

[Northwoods]

Thought maybe it was an outer ear corrector.  Use your imagination.

https://www.theparisreview.org/blog/wp-content/uploads/2016/03/xxx-d01-mad-alfred-18.jpg

[JoeCB]

Did you all pick up on "joint wiping" in the description?  Joint wiping refers to the joining of lead water service pipe. Until recently "wiping" was part of journeyman plumber training. I doubt that much of that is still done these days.

Joe B   

[Bill Houghton]

Did you all pick up on "joint wiping" in the description?  Joint wiping refers to the joining of lead water service pipe. Until recently "wiping" was part of journeyman plumber training. I doubt that much of that is still done these days.

Joe B

Mostly, people like to avoid lead poisoning, so, not much done anymore.

[amecks]

Yeah, Wow.  Now that I see what can be done with it, it looks like a real problem solver when trying to weld things.
Alfred E. (but not Newman)

[Sudsy]

Reminds me of a compass or dividers - with some pointed sticks clamped in it could mark out a circle or measure/mark lengths.

I'm leaning towards this
Footprint made/makes some high end cabinet maker tools.

The company is still around, you should ask them

http://footprint-tools.com/company-history/