Shrews.... It is impossible to know all the conditions a coin undergoes over the course of it's life. Anything from a person's sweaty pocket to being in the sun on an automobiles dashboard or any other countless variables contribute to the shades of toning we see on our beloved coins. Long and short is... There isn't an answer to your question! Could be anything.
I like Half Dollars. They just fit in the hand really well and I like the relief of the chicken ... I mean eagle. I like the 3/4 oz gold ones too.
Yeah it could be anything. I got 6 from the bank the other day. That's all they had and I took them. They all look in good condition. This one really caught my eye
It's a really tall design from the flat field for the height. If you compare it to modern coins the modern stuff is really flat, or at least seems that way.
If it has not been artificially enhanced, I think the color is just toning. On the clad halves, the inner core of copper is sandwiched by outer layers of copper/nickel. The nickel is what gives it the silvery appearance. This thin layer can be a variety of colors from silver, white, gray, gold and rainbow.
All coins will tone. It is almost unavoidable. We can conserve them best we can by controlling their environment.
I don't care for toning. Metals oxidize (rust) and that brings out a variety of colors. But many collectors like the different toning colors. There's all kinds of metals, with different colors.
I'm with Michael. I've never cared for toning in my own collection although I can appreciate the beautiful colors of a well-toned coin. I just prefer the natural silver/gray color. But some collectors love them.
Two radically different schools of thought, some think toning is wonderful almost no matter how bad most of us think it looks and some think blast white or grey (unless you consider 'old silver grey' to be toning) is the only acceptable color for silver or nickel alloys...and don't get people started on copper... I think most of us are in the middle, some light corr... toning is attractive, but can readily become ugly.
Personally, I don't mind some coloring. It's pretty nice looking on some coins. But when it starts transitioning to darker colors and turns blackish is when I don't like it and that happens right after a light purple (my personal limit). But I try not to buy any toned coins. They will just have a shorter lifespan unless they are preserved.
Anything created before 1985 should never be photographed with camera eye looking up at subject matter. Avoid the potential double chin...at all costs...