Due diligence

Due diligence is the set of checks a dealer carries out before buying a watch: confirming it's genuine and correct, that its papers match, where it came from, who is selling it, and what local rules apply.

Consistent due diligence is what separates a dealer who occasionally gets caught out from one who rarely does. It also creates a record showing you acted in good faith if a purchase is ever challenged.

Write your checks down as a standard routine and apply it to every purchase, including from sellers you know.