I have a 20 Francs/4 Belgas coin from Belgium, (KM 102). This is a large, 37 mm nickel coin with a weight of 20 grams. It has been defaced bij stamping with a die with lines (Reverse) and with a grid (Obverse). I think this was done officially, probably at the mint, to make the coin not current so it could be sold for its scrap value.
This coin was highly unpopular.The total number struck was: 18.979.000. The number returned to the mint was: 18.872.000. So a maximum of 107.000 (0,56 %) is still available. The coin was issued in 1931 and struck in 1931 and 1932, in both French and Dutch (Flemish) variants. It became without value on 1 december 1935. (information obtained from Jaarboek EGMP 2009 page 191). Defacing would have been done before this date.
I am interested in information about the, official defacing of coins. And also if other examples of these defaced Belgian coins are known.