Seated Liberty Half - Salt Water Damage?

The coin looks like the genuine article. Have you weighed it? It has little wear, so it should come in at 12.5 grams. Anything less than 12.2, I would be suspect. The spotting could be a result of contact with a reactive chemical.

This coin looks like a perfect candidate to be used as a pocket piece for awhile.

Wonder if the coin would benefit from a little acetone bath.

Here is a closer scan to the image after the acetone bath. The dark areas on the front do look a lot better than before. The pitting on the back really shows up with this latest picture.

Baking soda in boiling distilled water might take the spots off. In the microwave, boil a pinch of baking soda and a pinch of salt with 1 cup distilled water. I use a 2 cup, glass, Pyrex measuring cup. When boiling rapidly, remove the measuring cup from the microwave. Place the coin on a small piece of alluminum foil, and drop them in the hot solution together. Wait a few minutes and watch the spots disappear. The process can be repeated if needed, change both solution and alluminum foil. The solution allows the oxidation to transfer from the coin to the alluminum foil. Your brown spots will be gone.

I figured you probably knew the recipe. I thought I would post that for any newbies that were reading. Post some pics after you have done it.

I have never used acetone, I will have to give it a try. Have you ever used ammonia? It seems to work very well for me. It's what a coin dealer suggested. I haven't heard of or seen any negative effects. It works very fast on most grime, usually just a few minutes.

I have had some dusty yellowing occur also on some coins. I found that if the coin has been in contact with chlorine this happens. I am not sure if any other chemicals will cause this, or if anything in nature will cause it. I've been trying to figure it out also.