From the introduction of campaign setting book:
Treasure Hunter is a supplement for use with the D20 Modern RPG rules, designed to recreate modern-era, real world adventures. As its inspiration, it takes such motion pictures as RAIDERS OF THE LOST ARK, THE MUMMY and ROMANCING THE STONE as well as novels like KING SOLOMON’S MINES and the various tales of Dirk Pitt. At its core it uses the rules presented in the D20 MODERN RULEBOOK. When necessary, however, it makes certain modifications to facilitate adventures in the style of the inspirational sources mentioned.