I have identified my subject coin. It weighs 1.4grams and the diameter is 21.24 - 21.47 mm. The lettering that is legible is exact to the Numista description. It is not however silver. It is Bronze, Brass or Copper. I know that Austria minted !0-Kreuzer Bronze Coins in 1626. How do I find the KM # for this Bronze coin? I have a 6th edition 1601-1700 Standard Catalog of World Coins and have not found a way to locate this coin.
The coin you mention was .500 silver, so may look brown according to oxydation.
I have not found bronze strike for that period in Herinek catalogue but ...
Regards
Quand l'Histoire et la Géographie se croisent sur nos pièces de monnaie ...
Anyway, 3 Kreuzer coins were silver in 1626, though low grade as was mentioned above, practically billon. Improper cleaning could bring out copper from the alloy, which probably happened with your coin.
I collect coins and tokens which circulated in Africa from 18th century to 2000. I sell about 7000 illustrated world coins from http://www.avscoins.com.