Oh, it’s also a treasure map.
Well, it’s more a description of over sixty locations all but one of which are caches of gold or silver. The logical candidate for the source of them is the Second Temple but others exist. However, before you go get your shovel and metal detector consider these sample locations:
In the salt pit that is under the steps: forty-one talents of silver.
In the cave of the old washer’s chamber, on the third terrace: sixty-five ingots of gold.
I think this is a great item to use to kick off a campaign. Give your party of adventures descriptions of a large number of treasures that are obscure references. Make sure the list is also valuable to some other group and let competition and investigation get the sandbox rolling.
For example, imagine instead of trying to write your own Temple of Elemental Evil or using T1-4 that in the moat house in Hommlet the party finds a copper plate describing obscure places across the Flanaess where agents of the Temple stashed it’s treasure after the Battle of Emridy Meadows.
Now, instead of heading in the ruins of the temple they’re encourage to race agents of the Temple to regain the treasure. Perhaps this could include parts of the artifact needed to stop the Elder Elemental Evil. Certainly, it will trip up people familiar with the “plot”.