They are a testimony of the extensive trade network in the islands of the archipelago in the first millennium AD, thought to be connected to the Dong Son culture.
Even people in the eastern side of Indonesia, that had not shown any signs of contact with Hinduism coming from the Indian subcontinent, had developed sophisticated metal-working techniques.
Being hollow (because the two parts were combined into one), it may have been used as a water vessel, or hanged as percussive instrument, or simply acted as heirloom objects as a symbol of status in important ceremonies.
An exceptionally large axe discovered in Bogor have its swallowtail part adorned on one of its surfaces by a roughly drawn mask with bud-shaped eyes.
[9] Illustration of these axes carried by plumed warriors appears on various bronze objects across the archipelago and northern Vietnam, the origin of the Dong Son drum.