Are you in the right gear? Traditional Cache

Bridge Gear Park on Harbor Island houses some of the gears used in the original 1924 Spokane Street bascule bridge to West Seattle. That bridge was damaged when it was rammed by the freighter Antonio Chavez in 1978, after which it was replaced by the current high and low bridges.

You're looking for a magnetic key holder. The most difficult part of the process might be figuring out how to get to the adjacent parking lot if you're coming by car; bikes and pedestrians will have a much more direct route to the park. Park hours are dawn to dusk.