The Aachen coins are also zinc. I must admit I have some doubts about the citric acid. I'd try a wooden toothpick or a glass fiber brush (but that's hard to find) first. Also, dry thoroughly. The vaseline is for isolating the coin from oxygen, so no touchy feely afterwards, unless you put some more vaseline on the tips of your fingers. Make sure to read the list of ingredients of the vaseline and use only stuff that's really neutral and in particular contains no acids.
For protection of loose coins. I am keeping those little bags that say "don't eat me" in Japanese and that drink moist and come with things like electronics to keep them perfectly dry. The stuff has a name I forgot and you can buy it loose also. It's recyclable. When they've seen service, just put them in the oven with your next cake and they can go slurping again.
Peter
No they're not, they're iron - I'm pretty good at telling the difference, especially when I have them right here! That also explains the red rust rather than the whitish oxidation, and the fact that they jump when a magnet's about :-)
I also keep every bag of silica gel that I get (that was the name you were looking for!) and put them in with my coins, though unfortunately the bag with the Notgeld 2x2s was stored in a place that was a little too humid for a few years, and that may have caused the problem. The paper bag disintegrated first, which was a worrying sign ...
As an aside, I bought the 2005 edition of the Wenzel catalogue "Deutschsprachige Notmünzen ..." when it came out. Pity it's not illustrated, but it's a great reference book. And also worth considerably more than my entire Notgeld collection ...
Wenzel lists 28 different Notgeld types for Danzig (many with several sub-varieties and off-metal strikes), not just the two types of zinc 10 pf issued by the city and listed in the Schön Weltmünzkatalog, for instance.
Martin
NZ
