The Antique Shop Owner is a minor character who is first seen in the Dragon Ball anime, during the Red Ribbon Army Saga.

After a a boy stole Goku's clothes, Power Pole and Dragon Radar, he sold it to this man. The man, apparently knowing about the Dragon Balls, had forged a bunch of fake and fragile ones, realizing that he could sell them for a high price at his shop. This man lied to the boy and said the Dragon Radar was an almost useless object, only paying the kid 10 zeni for it.

Later, it is revealed that almost all of the things in his shop are fake and that he sells them to unsuspecting people for expensive prices, keeping the few valuable things to himself for his own selfish intents, and not paying much to those that give him the special objects. He also has a gun he uses to intimidate those that realize they are being cheated.

When Emperor Pilaf arrives, he sells him a fake (but very realistic) Dragon Ball and tells Goku that there were four stars on that ball. Later, Colonel Silver and his men arrive asking for one. Silver is not fooled and executes the shopkeeper before he can defend himself with his gun.

(Source: Dragon Ball Wiki)