Marks on Model 66-8 Cylinders

[NewGunDay]

Hello all!

I hope everyone is having a great holiday. I purchased a model 66-8 357 Combat Magnum recently and was finally able to shoot
It the other day. I noticed some "dots" on the front side of the cylinder. When I run my fingernail over them they do not seem raised or pitted. Does anyone know what these might be? A photo is attached.

Thank you!

Edit - I'm sorry that the photo is oriented with the barrel down. I am posting from my phone and it won't let me upload in the correct orientation.

 

[ralph7]

Looks like rust, stainless does rust, just not as much as regular steel.

 

[Pisgah]

If you look at the underside of the top strap you will see there is a screw hole for the sight that exactly lines up with the mark. The mark is a deposit of soot/fouling from gases that are reflected back by that hole. It is an often-noted phenomenon.

 

[ralph7]

I had never heard of that, but am certainly willing to admit my error if so.
The marks are certainly aligned precisely...

 

[dogdoc]

Very common with the newer(since early 1990s) drilled and tapped revolvers. All of my newer revolvers have it to some degree if they get shot

 

[9mmsubgun-m11]

Break Free CLP and a rag is your friend.