post office:

A post office is a facility authorized by a postal system for the posting, receipt, sorting, handling, transmission or delivery of mail.[1] Post offices offer mail-related services such as post office boxes, postage and packaging supplies. In addition, some post offices offer non-postal services such as passport applications and other government forms, money orders, and banking services.
The back rooms of a post office are where mail is processed for delivery. Mail may also be processed in other post offices that are not open to the general public.

They were partly motivated by the desire to provide reliable postal service for merchants and other foreign nationals in major cities, and partly by suspicion of the local postal service. The currency in use could be either the local currency, or that of the home country.