Karat weight question

[YoungMoney]

okay, its actually 2 questions. if a piece of gold is stamped 10k or 14k, is it not required by law to contain that amount of gold with only a little leeway? is it really necessary to test every piece for purity? has anyone ever seen gold that, once tested, did not contain sufficient gold to be stamped what it was? if so what are the odds of that?

also what does the stamping 1/20 12k G.F. mean???

[yadayada]

Generally, if something is stamped and comes from a recognized manufacturer, you're probably about 98% safe that it is as stamped. Most of the stuff you come across that is mis-stamped is wither from a custom manufacturer or is going to be plated or outright counterfeit, both of which are pretty easy to test for.

That being said, the amount of risk you decide to take is entirely up to you. If someone is trying to really game the system, they're going to try to pass of relatively large pieces as 14k, and not the little stuff like earring backings, feather-weight chains, etc. I'd certainly test anything and everything that is larger, because that's where you're going to lose the big bucks.

1/20 12k GF stands for gold filled, which means it is a layer of 12k gold over a base metal, and is no more than 1/20th 12karat by weight. Very common in old eyeglass frames, pocket watches, etc. Unless you've got access to lots of it, and plan on sending it to a refiner, you're not likely to find a buyer who will give you much for it.
Example: you've got 100 ounces of it - if it were 12k it would contain (more or less) 50 ounces of gold when refined. 1/20 12k GF would contain 1/20 of that amount, or 2.5 ounces of gold.