While I shouldn't have been shooting yet, I went back to my little range behind the house and shot a few rounds of low velocity cast bullets thru my 8x57/16 o/u. On the way back to the house, the front sling base,popped off the barrel and the gun hit the ground. THe stock cracked at the wrist, Damn. As I sat there staring at it I realized that there are, for want of a better phrase, liver spots on the receiver. Kind of like the ones on my hands. darker splotches, but no pits or other surface indents. Checked my drilling, a few, but not as pronounced. Same for my elsie smith. None on my Superposed, but it's blued. All of these are from the 30's or before.
So what are these liver spots? Oxidation below the surface?
Thanks
Bfly

Is the receiver plated?

Sambar,
It isn't plated, just a plain jane coin finish. Don't know if you can see it on this photo. These areas are only on the unblued surfaces.
Here's one of my drilling, where it is more visible. It's the darker area at the rear of the lock.

Thanks
Bfly

Sorry, my first thought was that if the receiver was plated, it could have been blemishes caused by solvent.

I think what you are seeing is what is left of long ago gone Case coloring!