If a dungeon has more then 20 items in its loot chest its considered to be a True Dungeon… True Dungeons are more likely to give you 10 000 coins or more and their chests may contain precious armor and weapons.
If you are in need of resources trying to raid a True Dungeon can be very profitable… But remember its dangers!!
I hope this helps.
Signed,
Dungeon Master Iomar