There is a one-shot adventure called Gorgoldand's Gauntlet, originally designed to be run with 3.5 rules.
The adventure mostly consists of a series of puzzles, traps, and a few encounters. However, the climax of the adventure has the players fighting a "Coin Dragon". After reading through the adventure, it does not seem to indicate a way that a group of characters can kill the dragon.
Most ordinary weapons do little or no damage to the coin dragon. Piercing and slashing weapons slide right through the loose objects in its “body,” doing no damage. A blunt weapon like a mace or club might dislodge a handful of coins, but these are easily returned to the coin dragon the following round. (They are sucked back into the creature’s body telekinetically.) A dispel magic cast upon the creature causes the disparate objects forming the dragon’s body to crash to the floor, leaving the dragon “bodiless.” The creature reforms its “body” the following round, but this allows PCs time to escape (possibly with an item or two from the hoard). The coin dragon is not permanently destroyed until it loses all of its hit points. The coin dragon never leaves its treasure room and naturally heals 3 hit points per day. PCs in combat with a coin dragon might find it necessary to do some damage, leave the treasure room to heal up and prepare new spells, then continue the assault later (possibly over the course of several days, depending on the strength of the party).
SQ—Construct: Immune to mind-influencing effects, poison, disease, and similar effects. Not subject to critical hits, subdual damage, ability damage, energy drain, or death from massive damage.
SQ—Resistances (Ex): The coin dragon has acid, cold, electricity, and fire resistance 5.
If I'm reading this correctly, it seems like any weapon attack with non-magical weapons are easily shrugged off. It looks like it's possible to deal magical damage to the monster, but it appears to be immune or resistant to most kinds of damage.
This is an encounter designed for a group of 1st level players. Given that spell casting is limited at 1st level, or that a party might not consist of an offensive spell caster, how is it possible to defeat this foe? Specifically, as the campaign was written, how was the foe intended to be defeated, or is it not intended to be defeated?