Hello, since I am currently interested in the Third Reich era in Europe (quite dark period of time with interesting coins nevertheless), I come across many coins not made of silver but other materials which were cheaper to obtain. This is the case with mostly all of German coins in this era, excluding 2 and 5 Reichsmark. Moreover, it is the case with huge number of counties that were under German occupation during WW2. I know that zinc coins are not made to be circulated long, more like emergency measure. Among others, I have few serbian coins made of zinc, and german 50 Reichspfennig made of aluminium: However, I am not sure how to grade them (there are pretty much worthless, but that is not important now). I found guides and videos on Youtube, but they are mostly on silver. For examples, the first coins look pretty bad (oxidation?), and the last one has some strange kind of corrosion inside 0 number and pfe letters. It seems I need to educate myself more about basic metals and chemical reactions In other words, not sure what is important when looking for coins which are not made of silver.
Unprotected zinc corrodes rather quickly when put in circulation. That's one reason current US cents with the zinc core are copper clad.
... and they still decompose before your very eyes. Some of those coins with the stains (ed?) look like aluminum. Will acetone work on those?
I don't think so. Acetone is good for oily contaminants, plastics, coatings and general crud. I don't think it works on metals and their oxidation products.
I just wasn't sure if all of it was oxidation. And even if it doesn't work, it shouldn't damage the coins. There are dips that will remove oxidation/ toning. But, aluminum and zinc being so sensitive will probably be reduced to a small green bubble of protoplasm.
Thanks. I was more interested in grading than cleaning the coins. In other words, it is still hard to determine which zinc, aluminium or bronze coin is worth having and which not. If it was silver, it would be easier, because there are at least some guidelines (level of detail, cleaned/uncleaned etc.)
I'm not sure there's a distinction there to be made. They're not going to grade with environmental damage. Your first step is conservation or else to try again with different examples. I collect Hungarian emergency and POW coinage from WWI/WWII so I've encountered a similar condition problem with zinc and iron coins. I've ended up with a near full set in MS63-64, but it took a lot of searching. With time I was able to find examples with minor surface conditions that could be conserved. These are volatile metals, so some conservation and/or protection of the surfaces is par for the course.
I don't do anything to aluminum to protect it. I use distilled water and then xylene to make sure it doesn't have any contaminants and then put it into a flip (or submit for slabbing). Light aluminum oxide is powdery and often will come off on its own. For zinc I use verdicare if there is light corrosion, followed by acetone, and then light machine oil.
The same way you would grade any coin. At first ignore the corrosion and grade the coin based on the amount of wear on the high points, that is you sharpness grade. then you can describe the corrosion and its severity. If you want a Net grade you then decide what grade for an UNDAMAGED coin would be worth the same as the damaged coin
According to the PCGS and NGC this would be an environmental damage and the coins would not be graded at all. Which basically means they should not be in any collection. I will try to look for better conditions, especially when it is about coins made out of cheap materials prone to oxidation. At least, I learned something new.
I don't care what PCGS or NGC thinks should or should not be in my collection. And yes they won't grade them, that doesn't mean that I can't.
That may be true, but being able to tell what would be properly graded and what will go under "environmental damage" especially when it is about lower quality coin materials such as zink, nickel, aluminium etc. (mostly of the coins in WW2 occupied Europe) is critical.
This is one coin out of zinc, German Third Reich military coinage, there is an oxidation on the rims, but the coin still looks good to me. It is interesting that it looks better in reality than on photos (probably because the coin is small and oxidation doesn't appear that much). What do you say?
