Coin

A Coin is the most basic and common treasure that is first found in Luigi's Mansion. There are 1536 coins in Luigi's Mansion, each worth 5,000G. Although they are the most worthless treasure, tied with the Red Diamond, in total they give you 7,680,000G in total, making them 7th most useful if all are collected.

Luigi's Mansion: Dark Moon
In Luigi's Mansion: Dark Moon, if Luigi captures a Greenie with normal power, he gets 3 coins as a reward. Coins can be also found in objects like in cabinets, under tables, or if one moves an object.

Trivia

 * They are worth as much as a Red Diamond.
 * In the beta of Luigi's Mansion, coins would stand up and spin around, similar to Mario games.
 * Coins in Luigi's Mansion: Dark Moon look more like coins from Mario games rather than Luigi's Mansion.