I have heard 3 of the 4 terms on that list.
German silver is used to denote nickel alloys. My firm stocks
nickel #752 in sheet and wire, composition is 65% copper, 18%
nickel, and 17% zinc. Melts at 1960degF. No silver, but a great
white metal choice where strength and wear resistance are
critical, like buckle and bola backs.
Alpaca is a term I first heard in Taxco, Mexico. Used to label
jeweler’s bronze, typically the whiter tones. We stock a base
metal grain called Bronwite. Not a whit of silver in the
composition, but still yields attractive castings.
800 silver is a reference for coin alloy, at 800 parts per
thousand silver. Up to the year 1964, U.S. dimes and quarters
were 900 silver alloy. Southwest Native smiths acquired their
metal from older Mexican pesos, having a silver content, 800 I
believe. Coins will vary by region and date of production as to
actual silver content.
Austrian, I must pass on. Assumption indicates, since Austria is
in the German neck of the woods, that the term Austrian silver is
Indian Jewelers Supply Company