"Z", no it's German silver or Nickel silver. .050 thick, 16ga. (Brass with 18% Nickel content) I have made some from Sterling bit the silver for this size piece runs about $75 as opposed to $6 for the German silver, so most folks opt for the German.
Besides, Sterling wears, whereas German Silver is tough and can endure daily handling without showing any wear for years and years.
Silver is much easier to cut as the German is wearing on gravers. Nickel is very abrasive and often you can feel tough spots when hand pushing. The brass and nickel doesn't blend well and can be gritty in places.