1711 3 Kreuzer Coin - Poor Condition - How Was It Made?

Nice old 1711 3 Kreuzer of the unlucky Joseph I of Austria (styled here as Archduke of Austria / Duke of Burgundy and Silesia.) Be careful when handling it, they will crack and break quite easily.

I believe these were billon -- a base metal/metals (usually copper and/or tin) alloyed with silver -- and by 1711, while a very few were hammered (planchets between two dies, with the top die being physically struck with a hammer) most were struck using early coin milling machines -- screw presses in Britain and France, eventually Spain, and roller presses in the Holy Roman Empire (including the German States & Austria coinage such as your Kreuzer.) The roller press literally rolled a planchet strip between two rollers with die impressions, and the resulting planchet was then cut out, often by hand, from the strip. The result was often irregularly round to elongated coins with rough edges and mushy, uneven "strikes." By the late 18th c. the screw press was widespread, resulting in coins with more uniform roundness and superior detail.

In your case the silver has probably crystallized over time due to age and is liable to fracture easily, causing a layered or crystalline appearance to the metal as well as resulting in the separation of the alloy into its component metals.

This is based on my own knowledge; a bit of research from Google would probably prove quite illuminating.