What you see before you is the attempt to make the collection metadata for the IMA accessible in an extremely simple format.
Each json file represents a single work of art. The objects are sorted into folders by zero-padding their unique identifiers (irn).
Given an objects unique identifier, you can load its webpage with the following URL template:
http://imamuseum.org/mercury/load-artwork/{irn}
Image information is coming soon, but you can easily grab the URL of the primary image for an object using the CSS selector img.primary-mercury-image on the objects webpage.