What is this square metal plate with a handle?

Question

Found this piece of equipment (?) left behind by a previous owner and am trying to figure out what it was used for.

It's a thin, square metal plate with rounded edges. It's maybe 14 by 14 inches. On the bottom is a piece of wood shaped as a handhold and a thick rubber ring.

On the top are concentric circles of a thin wire. The wire forms disjoint circles, not a spiral. There are 11 of them.

My two guesses (neither of which fully makes sense) are

1. Maybe it's some kind of tamping or stamping tool? But it doesn't have any grout, mortar, or concrete residue on it.
2. Maybe it's a radio antenna that you walk around with while listening for a wildlife collar? But it isn't clear where you'd clip any wires.

Answer 1

It is called a hawk. It is used to hold drywall joint compound (mud), plaster, mortar or other materials of similar consistency. It is also called a mortarboard. The hawk name seems to come from the way the board sits on your arm, like if you were training the bird.

The rubber ring is there to protect your knuckles as you work with it day after day. The concentric circles are there to prevent the material from falling off easily.

It is held in a manner similar to a painter's palette. What makes a hawk better than regular mud pan is that your arm is holding the weight, not your fingers, causing less fatigue. It's also a lot easier to scrape and clean. Since a lot of drywall and plastering work is spent cleaning your taping knife, having 4 long edges to scrape the knife against speeds things up. (Note that some people make a distinction between a taping knife and a joint knife, others don't)

Answer 2

Not plane, nor bird, nor even frog. 'tis a hawk. Put a glob of drywall compound on it and carry it in one hand as you apply the compound with a knife in your other hand. In some ways better than a pan if you get the hang of it. Here's a youtube video to give you an idea of how it's used.