Gold (K= karat) (P= Plum) Plum is high quality (purity) when a P is added. (example 18KP)

     10K......41.7%pure

     12K......50% pure

     14K......58.3% pure

     18K......75% pure

     22K......91.2% pure

     24K......99.9% pure

     Gold Filled Markings (W1/20 14K G.F.) what it means: W=weight,

     1/20 = 5% gold, G.F. = Gold Filled. Gold Filled is 300 times
     thicker than gold plating. Gold filled is bonded to brass or bronze with
    (fusing)  heat & pressure. By law 5% of its total weight must be gold.

     Gold Plating:
     Thin coating of gold over a base metal (Electroplating) A gold plated
     item will be marked 18K or 14K HGE (Heavy Gold Electroplating)
     Gold plating is 7 - 100 millionths of an inch thick.

     Silver:

     Sterling is 92.5% silver, 7.5% copper

     Sterling Markings are .925, STER, STERLING.

     Sterling from England are marked by a Lion Hallmark.

     Silver Filled items are marked 1/20 silver filled.

     Vermeil is sterling silver covered by an electroplating of gold.

     Platinum:

     Markings are PLAT, or PLATINUM, and maybe marked .900 or .950
 
 

The Online Encyclopedia of American Silver Marks
British Silver Hallmarks