This glass bottle was made by blowing into a mould. New types of decorated mould-blown glass were being produced in the Roman world by the third century AD, and were to remain in circulation for over a hundred years. Many examples were made. Although particularly popular in the eastern provinces, a number of types of mould-blown glass bottles are found in the west: new and larger versions of grape- and head-flasks were produced at Cologne in the Rhineland, Gaul and also Belgium where part of a two-piece mould for a grape flask has been found. These western glasshouses were also responsible for a series with the body of the flasks or bottles moulded in the shape of a deity or monkey (perhaps itself a caricature of the god Mercury). This fish bottle belongs to this series and is comparatively unusual, though it is not the only example. Fish are only occasionally depicted in glass, but at least one that was free-blown is known from Syria. Fish are also added as applied decoration to a fourth century AD vessel from Cologne.