My point exactly. People do all kinds of things to coins. There is no way to know why they do what they do unless you ask them.
failed attempts to create errors, is what I think on some coins. the coins I have seen closely in detail, look as if there is some that been done by a professional or familiar with errors. then other coins are done by a non experienced error person. that's my theory, of course there are many other theory's, also.
@teachmind, thanks. I just used the other two as a frame of reference for the color. @Kaos, it weighs approximately the same as a "normal" 1957-D, give or take 50-80mg
I don't think proof are made from extra thick stock. The square rims may make them look that way. The OP coin looks plated.
I don't think its gold plated. I have seen these occasionally in the past. My guess is cleaned with some kind of 1960's burn your nose and give you cancer chemical concoction.
Gold plating or some other plating. It was very common on these in the 50s and 60s....similar in reason why you can find scads of gold plated state quarter sets out there. Profiteers looking to make money off of people who don't know what they are buying. Someone buys these *24 Karat* gold plated sets thinking they are worth tons of money, to find out one day they are worth-less because now they have a damaged coin that will only spend at face value...Some people will collect the plated sets tho. I've sold a couple for a bit over face and made a buck or two. To each his own. @RobRobyn - As a committed forum member, collector, numismatist and enthusiast, here to learn as much as I can from others who know more than I do, I apologize for the above quoted "muddying of the waters." There is no such thing as an professional or non professional error person or maker. An error can only happen at the mint, up until the coin leaves a press, anything that happens after that is not an error...it's call circulation at best, but Post Minting Damage is really what it is. Plated coins are PMD, a coin altered after it leaves the mint.
It's gold plated. Someone did this as an aftermarket gimmick to sell coins. I've seen dozens of them, I still have some in their original packaging. Fun to collect but only worth a penny