I have seen many a pocketwatch auctioned on Ebay that say nothing about the case. So here is a list of what to look for:

Warrented 10, 15, 20, 25 Years or 14k GF, Rolled Gold, or 14k RGP: This case is Gold-Filled

14k, 595, 590, or .59: This case is 14k gold (also goes for 18k gold: .750, .75, or 18k)

Silver, .800, .925, .600, Sterling, or Coinsilver: This case is silver

Silverroid, Oresilver, Silverine, Nicklesilver: These all contain NO SILVER, these are nickle or tin based metals.

Brass: No markings or will be stamped BRASS inside

Copper: never used as a case metal