Muddy key

Muddy Key is a free-to-play item on the OSRS Grand Exchange in the other category.

In-game examine text: "It looks like the key to a chest."

It has a Grand Exchange buy limit of 11,000 every four hours, a high alchemy value of 48 gp, and item ID 991.

View on OSRS Wiki

Muddy Key shows an active flip setup with a margin of +271 gp and 900 trades over the last 24 hours.

At the buy limit of 11,000 every four hours, max profit per cycle is about 2.98m gp — high margin with healthy liquidity.