It is aged in barrels. When one uses the term "barrels" I assume they mean barrels that are made of wood.
If made of plastic or metal they would be called vats. Of which plastic was probably not available in 1923, and metal at a premium between two World Wars.
If made of plastic or metal they would be called vats. Of which plastic was probably not available in 1923, and metal at a premium between two World Wars.