I've attached a photo for you all to look at regarding my question, maybe a stupid question to you all. But humor me.
I've seen these scratches a few times on the inside of case backs. Circles trailing off from heavy scratches trailing off to light circle scratches.
What causes this?

You are lucky because sometimes it even gets to the point of gouges. Sometimes a movement screw will back out so when a person screws tbe back off or on as it gets closer to the screw head it will gouge the case inside. Most of the times you see this near the edge where the case screws are, the one you show is toward the center. Without knowing the movement that was in the case it would be hard to guess what other screw might have done this. That is my initial guess, hope it helps.

I see. And maybe someone put a movement in the case that wouldn't fit.

The saddest part of these defacetory gouges caused by loosely assembled case and movement screws is they are completely avoidable. Often I muse that the watch repairer who did this and then crunched the case cover back on with full knowledge that it was NOT right must have been in a big hurry to "attend to other business" at the Acme Saloon next door.

I usually call them blacksmiths, David. When they're not shoeing horses or mules, they're working on watch balances. Requires the same touch, or so they think......

I was once told that that particular type ground in swirl inside a back can be caused when the screw of a main spring barrel becomes loose and starts to back out. Everytime the watch is wound, it acts like a lathe and cuts into the back of the case.

When the case back was finally opened, it caused the scratches to the side you see next to the ground in circle. If you note, they fade off to the right, which would be the direction the back takes when it's being unscrewed from the case.

I once found those exact same marks in the case of a 992B I had, and it was a correct model 16 Hamilton case, so it wasn't due to a wrong movement in a wrong case...it was due to the barrel screw backing out.

Regards! Mark

Sometimes like Mark said they are made by the winding mechanism, sometimes the case back has a dent or is bowed in slightly and will rub against the winding mechanism.

LIKE THIS?

Thanks for the education, guys!
jeff

PERFECT, Jeff!!!!