This is from My Treasure Spot:
"14K gold is 58.3% pure, although it is usually marked in decimal as 585. Now, if it's marked as "14K", it could actually be off by up to half a karat of purity, or 2.08333333% in purity. Gold marked as "Karat Plumb" or "KP" is exactly that purity. I have a 10KP ring, so it is exactly 41.7% pure gold."
"I can't remember what the exact ratios for rose gold and white gold are for the different karat ratings. However, those ratios do change for each different karat value, as you are using different amounts of gold. Rose gold is created by adding more copper to the mix of metals alloyed with the gold. White gold is made by using Nickel (which is also why white gold has a lower conductivity than yellow gold). You can't really get rose gold and white gold in purities higher than 18K, as the amount of pure gold tends to by to much for the other metals to affect the color."
"Anything marked as "HGE" (heavy gold electroplate), "RGP" (Rolled Gold Plate), "GF" (gold-filled), and/or "GS" (gold shell). These all indicate that the item is plated, not solid. Many times, the "RGP" and "HGE" will also have a marking that reads as 1/40 14K RGP, which translates as "one-fourtieth of the total weight of metal is 14K" "Rolled Gold Plate". I have a couple like that. I also have a couple marked as "18K HGE", which just means that it's plated with 18K gold, but doesn't specify of weight of the plating."
"Be advised that in the past, and even to this day, there are unscrupulous people out there that will cheat to make a buck, and pass off fake marked jewelry. Many relic hunters have wedding bands marked as "18K", but in fact were plated brass. Some modern jewelry from other countries is also plated junk. This is where acid test kits come in handy."
I hope this helps to clear things up for you!