Sack that may be a bag of holding

In the Ruins of Castle Karn, a location within TSR AD&D 1st ED Module N2 - The Forest Oracle that the druids sent the party to investigate in return for a cure to take back to The Downs, there was a treasure stash, amongst this was a sack that appeared to be a Bag of Holding it seemed to hold more than it should and everything was still accessable that went into it, many thousands of copper coins were loaded into the bag and the party left with their loot.

Unknown to the party was that this was a different kind of magic bag that only functioned like a Bag of holding within the walls of the ruins, the enchantment on the bag turned anything contained inside into useless bits of garbage once outside the walls, I dubbed it "The Bag of Encrapination".