Over on Ethnographic we are looking at Powder Flasks and Containers ...I found some interesting artwork relevant to the European angle. Joseph Wright of Derby in 1769 illustrates a plain undecorated form common in English style.
In the item below: Matching pistol and flask, German, probably 1579, both decorated with finely carved antler inlay...Sometimes we forget the pistol where a small powder flask is engaged... in this case the weapon can be carried fully loaded...Clever !