Always demand delivery or physical product at time of sale.
Never pay cash. Caveat emptor and “if it sounds too good to be true” it probably is. Beware of any one to tries to sell you the golden path to easy riches.
It's truly astounding that people buy gold and silver because their inherent value make it safe. Then they decide to put it in a vault somewhere with just a certificate to "prove" it's being held for them.
What's the point of buying gold and/or silver if you don't physically have the gold and/or silver in your possession?