I have searched and searched and can't find an example or description to compare this to. I'm sure it is another form of MD, but it doesn't look the typical MD I see pictures of. I just noticed as I uploaded the pics that it has the same effect on LIBERTY and the back of the portrait on the obverse, which is the exact opposite side of UNITED. Can someone tell me what this is called or how it is caused?
If your describing the greenish colored type of contamination, your asking about Sulfating types of problems. All Copper is effected by Sulfur in the air by the process where Sulfur rich coal has been burned in factories or power stations. Also, Volcanoes emit Sulfur into the air. Usually this is in the form of Sulfur Oxides. Mixed with the air, it becomes an acid and attacks many substances and Copper anything is one of them. In many areas if you look at Copper piping, you'll also see similar greenish contaminations. And in some areas the amount is so high it is known as Acid Rain and has ruined many statues. The usage of Copper Ground wires in the ground by organizations in such areas also has proven to be a disaster. After some time all the ground wires and ground rods have dissentigrated into Copper Sulfate. Just normal for many coins to get that stuff on them.
No, I'm looking at the "shadow" of the TED and first S. It looks like MD, except that rather than the flat shelf look, the letters are "dug in". It has the same effect on the obverse in this exact location on the coin.
It looks as though there may be a die crack coming from the corner of the Lincoln Memorial, and extending between the "I" and "T", and may have something to do with this shadowing. The die may have been past its useful life at the point this cent was struck.
Here's the obverse It looks like there is a die crack in the pics, but there's not. The doubling is "cut out" rather than raised. Here's a closer look.
I think it is die fatigue. Ihave a 1957 where the 7 has a shadow. Only thing is yours is covered in letter shadows.
