Yes if you can read German, the Kurt Jaeger German coin books and I'd bet the Polish coin book by Gumowski
Yes, I can read some German, but not Polish. I'd have to visit friends in Wisconsin to read me the Polish. But then again, I wouldn't get much translated because of the beer, sausages, and live reenactments of the Green Bay Packers highlights of Super Bowls I and II.
I like seeing these with rust on the surfaces. That is how they should be. There were some really good modern copies made of these with pristine surfaces that got past the TPG's in recent years. NGC is still trying to buy them back.
Be careful not to "throw out the baby with the bath water" to use an old saying. These were not issued rusty. Nice genuine examples exist. Rust spreads and endangers other coins. If the illustrated coin was mine I would remove the rust and coat the coin with clear nail polish. I can live with the pitted surface.
Such coins were released at 1916 in Berlin Mint and Hamburg Mint for an appeal in western part of Russian Empire (occupation zone of Germany). There were 3 face values: 1, 2 and 3 kopeks. All of these coins were made from iron.
