4-1/2" O.D. 1-1/2" High

I ruled out leather Pig Castrator and Miniature Biker Flying Saucer.

Autobody tool or palm thimble? no idea?

bung plug for democrats,

Looks a lot like a pouch full of sand or shot that we used to keep large maps stationary on a drawing table or light table with out using tape or tacks.

What's on the reverse side?

Reverse side is identical

I go along with "1oldforester", an old map/plan weight.

It is a fine metalworkers bag. Used while shaping or embossing thin metals.

Moosetrot

This sounds correct

I say it before anyone beats me to it.... pig castrator.

Yup,,paper weight.

Hockey puck!!!

You need two of that model to have an effective pig castrator. Bang them together.
Jim

Shot bag. As said above, used to hold stuff down. Maps, parachute packing (DON'T leave it in there!!!), sewing, other thin rolled materials, etc. Usually filled with lead bird shot. They make good stress balls too.

Just watched a You Tube video , a jewelry artist was using one similar to shape a thin copper bowl. She said the more you hit it the softer the bag gets... so I'm not ruling out pig castrator also.

Looks like a weight to me..I use various weights just like it to do leather work. In my days of metal working all my shot bags were larger and softer...like press your fist into it soft. If it was a metal working bag I’d say maybe, maybe for repousse before anvil work.

What does it weigh?

Good timing AKAjust- I'm cutting up venison so here it is: .8 lbs.

In the map room here at work....

I could easily see map weight or shot bag for metal working, here's the shot bag from the Jewelry Artist

I use a larger size of that very thing when building rounded sheet metal parts for cars. Just called a shot bag, but could be used in that size for the map thing too. The small size of it would be much handier for small parts like jewelry work!