Ran across this coin today and decided to buy it. I've always summized this happens when the planchet mix is uneven. Anyone else have a different theory?
Looks to me like a coin that was cleaned but the job was done poorly. Something like not being well rinsed. Poorly mixed cent alloys generally results in a wood grain appearance. You see it to a lesser extent with nickel alloys. Never seen it with silver or gold.
I doubt that is a mixing problem. All I have ever seen with an alloy problem, the "problem" goes completely through the planchet. I think you are looking at the results of simple environmental causes.
I definately don't attribute this to cleaning. In hand this coin is full of luster and it cartwheels. Perhaps I'm naive, but every cleaning process I've seen removes the luster and the coin no longer cartwheels. Also, if the coin was dipped, it would affect the surface evenly unless there were variations in the planchet mix. I've seen this same thing on other BU Lincolns, as I'm sure other experienced collectors have as well. rlm - I have to respectfully disagree on the mix problem always going through to both sides. I don't have a picture, but I have a 50's cent that clearly has a high zinc concentration on parts of the obverse only (silvery appearance), the reverse is normal. When the alloy is uneven the surfaces will oxidize and tone at different rates. I agree there was an external environmental influence, but I would expect that to evenly affect the surface if the planchet was homogeniously mixed.
For the time being I'm going to stick with "cleaned". A quick dip, especially in a diluted solution, can easily leave the "cartwheel" behind. I still believe it was dipped and incompletely rinsed. [My opinion subject to change.]
First, I see nothing to indicate to me that the coin has been cleaned. As for the alloy mix, this coin is not from the 50's and it is not silver. I have seen what you are referring to maybe back to the late 40's, but not earlier. That coin you have just does not look like anything I associate with alloy mixing. Every one I have or have seen, it is the malformed brassy looking alloy that does not turn brown like a properly mixed alloy (usually surrounding) does. On my 23-S, the graining virtually disappears where the coin has it original red. The closest I have to a coin like yours is a 13-D that may appear similar, but it is two shades of brown and not the red and brown you have. If you look at my 13-D, the boundaries between the colors are just not the same. Yours are pillowy and mine are kind of jagged. The only thing on your coin that even remotely reminds me of alloys is at the "e pluribus"
Indeed...good observations. Perhaps I'll look at this coin using the SEM at work to get an idea of what elements are present in the dark area versus the light area. Great discussion, thanks for participating RLM.
Having never used a SEM, just what would you expect to see? Now we used to used a (I am blank, but it measured X-ray bounce) to determine metallic composition. Now that should show something were it the mixing.
I have an SEM with EDXRF in my lab. I will be able to look at the elemental composition on the surface at any point on the coin. :kewl:
Unless, it was due to a liquid that contaminated the surface of the coin. And based on that way that coin looks, that would be my guess as to what happened.
I've actually made coins that look alot like this by accident. I keep change, mostly cents, in the cup holder in my car. I get a coke at McDonalds and set it on top of the coins. As the cup sweats, it runs on the coins. After a couple sodas, some get this type of pattern on them.
I agree! It appears that some type of liquid flowed over parts of the surface of the coin or it was in an envelope or album that got wet. Frank
I'm ready to kill my boss when he gets back! LOL He was the last one to use my SEM and he had it so jazzed....arrrggg....I didn't have time today to get all the settings corrected, busy day...but...I did toss it on for some quick-n-dirty. It does indeed appear to be a stain. The levels of Cu, Sn and Zn were the same in the darkened areas as the clean areas. In the darkened area, there were higher concentrations of C and O, indicating oxidized organic material. Just above the E.PLUR, I was picking up sulfur, it's the only place I found sulfur, so that area is toned. I wish I had time to get the picture better and the EDXRF graph corrected. The knucklehead changed the element intensities on the graph to blue so they didn't print out. I'd have to fiddle with it to get it back to white...no time...so...the height of the elements on the graph relate to intensity (concentration).
Thank you for posting that. I think I understand what your pic.graph in showing, but what are the spots? i.e. top tip of the "C", back of the "E", behind eh "C", etc.
Most likely those are hits on the coin. Remember, what you're seeing is not an optical image, but the backscattering image from electrons. The picture would normally be a lot clearer, but my boss was fiddling with the instrument last week and he has everything jazzed up. It's a VERY complicated instrument to operate and it's going to take me a few hours to get it back to normal.....I just didn't have time today. All I was interested in today was the EDXRF scans.
A couple do correlate to (or at least seem to) dings that I can see on the coin, but most seem to be random. I was just curious if there was something it was trying to tell me.
