1 {scene: In the tavern. Still.}
1 Mordekai: The Duke is offering 5,000 gold pieces for the recovery of the Ruby of Dwarven Might? Is that all?!
2 GM: Well, he'll also let you keep any incidental treasures you may find...
3 Mordekai: Let us? How is he even going to find out? I'm certainly not telling him... guys?
4 Alvissa: Uh uh.
4 Lambert: Not me.
4 Kyros: No way.
4 Draak: Draak know not of more loot.

Yes, that's a TSR Dungeons & Dragons Fantasy Adventure Game Expert Rulebook, 1981 edition.

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2013-07-06 Rerun commentary: This was a slightly confusing thing about some traditional D&D adventures. You'd get some job which offered a certain number of gold pieces, plus you could keep whatever treasure you found. As if the guy who hired you would ever find out how much treasure you found!

The other thing was the tax collector, who would attempt to assess adventurers for their "income" (i.e. treasure they'd looted off monsters). This was in some places recommended as a way to prevent PCs from getting too rich. Presumably these tax collectors must have had magical powers or something, because as sure as the sun rises none of the adventurers would ever admit to having found any treasure.

Imagine if your local government tax office had magical powers of auditing...