The office on Deep Space 9's Promenade where valuables are weighed, valued and held in safe keeping, used by traders, visitors and anyone unwilling to trust Quark with their property.
The assay office is one of the public services of the Promenade, a secure room where goods brought to the station can be appraised and locked away. It is staffed by Bajorans and falls under Odo's watchful protection.
It features in Q-Less, in which the archaeologist Vash, newly returned from the Gamma Quadrant, deposits the artefacts she has collected there before trying to sell them through Quark. One of them, a crystal, turns out to be a living creature that is draining the station's power.
The office is referred to in several other episodes as the proper place to store latinum and valuables, and its lockers are an occasional target for thieves, which gives Odo further reason to keep an eye on new arrivals.