It is generally accepted that metal, stone and ivory sculptures of this form of Avalokiteshvara are far posterior to the original sandalwood icon kept at the Potala, made by a Nepalese artist in Tibet or Nepal and dated 7th century. This copper image, however, has all the characteristics of the Nepalese Licchavi period and looks very much like a Vajrapani kept at the Cleveland Museum, and another kept at a temple in Kathmandu, both dated 8th century.
All three wear a similar necklace and snakelet armbands high up on their forearms, which we have also seen on a 6th-7th century wooden Avalokiteshvara from the Freer and Sackler Gallery.
At the same time, there is no doubt that this is Phapga Lokeshvara but with added jewellery (other than his usual earrings) …
… and without a banana-like hair bunch sticking out of his mitre-like crown. We saw a similar headdress on a 15th century circa Tibetan wooden image (reproduced below for comparison).
Both have an effigy on the front panel of the crown, not of Amitabha, as may be assumed, but of Phagpa Lokeshvara himself (a feature specific to this form of Avalokiteshvara).
We are therefore looking at a (so far) unique metal version of the Potala image made more or less at the same time.