What is this?

[BigV]

What is this?

No pictures yet, it's at home, I'm not.

It's a scratch built thingamjig, yellow grounded AC plug, very heavy gauge power cord into metal single gang electrical box, a light switch, BUT the throw is perpendicular to the long axis of the box. The other half of the box has what appears to be a metal cover over a transformer. Other side of box has two approximately 16 gauge twisted core wires coming out, through a tight rubber grommet. These are about a foot long, and are covered with a length of shrink tube. They go into a black plastic encased toroidal electromagnet.

I plugged in the power cord, turned the switch on. The torus displays magnetic aspects. I tested it with a screwdriver. When I put the tip of the screwdriver across the hole, it seemed to vibrate like a buzzer might. Weird. When I inserted the tip of the screwdriver into the hole it was pulled strongly into the hole at first, but when the screwdriver got about halfway through, the pulling force stopped. When I tried to withdraw the screwdriver, I felt a little resistance at first, then an increasing pull countering my pull, strongest just as the screwdriver tip neared the "exit".

Like a solenoid.
So, wtf is this thing and what was it made to do?

I have some ideas, but I don't want to prejudice the jury of my peers. Or betters!