The Gold Brick Scam, Curate's Egg
The con artists, a group of miners, approach a rich man, such as a banker or business person, with a problem. They have been paid with a brick of gold and none of them have any actual cash. They ask the victim to buy the brick from them at a bargain price. The victim takes the gold to be tested and, cutting off a corner, finds it to be pure . He pays the men, who quickly leave.
The gold bricks is only partly gold. The centre of the brick is just a square rock with the corner's removes. This rock is covered in gold to look like the real deal. However, since the miners are in a hurry, they rush the victim into testing only a small corner of the gold.
This may sound like the kind of scam that you are likely to never run into, but a quick change in scene can change this. Imagine you are buying perfume, and the seller lets you try some, you like it and buy some. When it's opened at Christmas it doesn't quite smell like you remember. The con-man has put cheap perfume in an expensive box, and convinced you into buying it by letting you smell what you think you are buying.
This is a clever scam as it convinces the mark they are getting a deal they know is good (unlike in coin collector scam). But doesn't involve an actually switch. This scam has made a comeback with online shopping. A lot of the time you are buying just by looking a picture. Be wary, the picture may not show all.
Depends on what is for sale.
How to avoid being scammed
The old saying, 'if it's too good to be true, it probably is' works a treat here. As in cards you should always cut the deck, in life you should always check the box when buying from an unknown source.