My favorite coin.

I bought it in 2005 at a flea market in Dąbrowa Górnicza on the third Sunday of April, a week before my name-day. The coin was locked in a holder on which the price was written in pencil. It was a cheap present, I paid PLN 10.00 (about $3) without haggling.
That unusual dime changed my life - no exaggeration. I have been collecting coins for over fifty years. In the last dozen years or so, I think it has become more than just collecting. When my collection reached a certain "critical mass", I decided that it was worthwhile to start sharing my own insights and thoughts with other coin enthusiasts. This took place on numismatic forums (Allegro, E-Numismatics) and on the pages of “Przegląd Numizmatyczny”.
The purchase of a 10-pfennig coin of the Kingdom of Poland with a partially doubled reverse encouraged me to take a closer look at the coins of this period. It soon became clear that the 1917 10-pfennig coin is not only two cataloged variants, which differ in the distance of the reverse legend from the edge.
Why was it not noticed earlier that there are two variants of the rarer coins, which differ in the shape of the numeral 1 in the denomination? Why did no one notice that the feathers of the eagle's neck on the obverse of some of the coins are ruffled, while on the other coins they are lowered?
Probably the reason was the disregard of such common and inconspicuous iron coins. Over the course of a year, I collected a considerable number of coins of the Kingdom of Poland which showed visible differences from the "canonical" original. It turned out that on almost all denominations there were drawing doublings, sometimes very dramatic. I was also astonished to find that the 1918 1-pfennig also existed in two variants, one of which was based on the extremely rare 1917 coins. One year was enough to collect the material that allowed me to develop and publish a specialized catalog of coins of the Kingdom of Poland.
The painstaking examination of hundreds of coins at bourses, shops and auctions, as well as inquiries among collectors, made it necessary to develop the second edition (2008) less than two years after the first (2006), which also became outdated with time. The third (2014) and fourth (2019) editions were produced. All in Polish language.
Coins of the Kingdom of Poland are of equal interest to Polish and German collectors, the former considering these issues as precursors to the separate currency of the Polish state restored in 1918, the latter as coins of the "German dependent territories". Unfortunately, I have a very poor command of the German language. So I decided to publish an English version of the catalog.

You can order the catalog at Amazon.de
https://www.amazon.com/POLISH-COINS-191 ... B0BVTLQY3F
Jerzy Chałupski