Since I first wrote this, I have gathered additional information on the 2 major national advertisers.  I have kept part of this original post up, however its not so much as the check scam, but the companies themselves.

It used to be only a couple companies would gather a panel of experts and travel around to various cities to book hotel blocks and buy valuable small items from those who brought them in after reading advertisements.

Today that seem to have exploded. To over a dozen and a half national advertisers willing to buy your 'Old Gold' 'Unwanted Watches' and 'Anything Valuable'.  Their advertisements out lets include Television, News Papers, Billboards, Email, Online Search Ads, and Mailings.  This irresistable means of putting your hands on cash instantly has lead to scammers able to hook prey and swindle them not only out of their gold but their bank accounts as well.

Rule of Thumb: Do Not Mail Valuables to any 'We Buy Gold' centers.... You can get 'instant cash' at any pawn shop or coin shop near you!

You plave your broken unwanted gold items into an envelope and mail it off to a town in Florida.  They 'evaluate it' and send a check in a week or so later.  You may be happy.  But say you know gold they way I do.  If gold amasted to $400 (actual spot value) that check may amount to $60!  If like me you'll call them right away, and ask for your $#!* back! They'll explain they could doctor your invoice e.g. make 10k as 18k and add a couple pennyweights and give you a counteroffer of close to half the actual value. In this example $180!  ...Had it been taken to a pawn shop the offer would be $180,  My personal offer would be $275,  eBay you may get 85% or $335.  For this particular company you need to send them half-a-kilo of 14k gold to get 60% value (most likely that would be a pawn-shop that knows no better)  Such company also has a direct deposit option.  This option should be avoided as when you refuse the offer you have given up your chance to renegotiate counteroffer.

Recently a postal worker had been nailed for stealing the gold kit packets from mail recepticals.  Though the packets are considered 'fully insured' however being reimbursed may be next to impossible if the packet hadn't been entered into their system, that is at the post-office. 

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One such scam:  You reply to an e-mail and they send out a 'free mailer' to pack your gold into and send in.  A week later and the check arrives seemingly higher than what you expect.  Say $3500 for something that should be only $700!  The paper along with the check may give you a choice of a part-time job that instructs you to cash the check immediately then wire transfer $1500 to some bank account, buy $1500 worth of gold jewelry from a local pawn shop and mail that to an address (at which they'll send you another check probably before you mailed off the gold) You keep the remaining $500.  If you say no for the job, you keep the $500 and return via wire transfer the $3000.

And as you guess it, the check is a fraud.  The check may be of a nationally advertised 'Gold Buyer' with bank routing and account # on it, but that company will stop payment on it two weeks later.  Thus could not only be out of your gold and valuables, but also a negative balance at your bank.