Starting a black cabinet is a lot of fun. :-)
Any number of alloys are employed nowadays by counterfeiters, and in some cases (for rare dates) they even use actual silver. For lighter metals, however, they tend to make the planchets a bit thicker to compensate.
I'm actually getting around to documenting and numbering mine on the Numismetrica Blog (link in signature), but these are primarily
US coins.
On the blog I'm going over a number of criteria (magnetism, diamagnetism, ring, weight, diameter and thickness) as well as any other readily identifying marks (if it's a fantasy date, die markers, etc). If you want to, if you can get some nice pictures of the obverse and reverse and fill out the sheet, I can include what you find in the listings.
One of the dealers I get counterfeits from was recently marauded by a number of fake silver yuan. I'm considering grabbing them the next time I go in along with the usual US counterfeits. :-)