This frame is in the form of a Canaletto frame using low relief carved timber, characteristically worked into a shallow ogee profile (or ovolo, as here) at the corners and centres leaving unadorned panels in between.
This frame is not the first presentation of the painting. It appears in a Louis XV revival swept edge frame in a photograph from 1918. Given the painting came into the collection in 1910, it is likely the Canaletto frame was put on the painting by the NGV sometime after 1918.
See also Canaletto frames on:
George W. Lambert The official artist, 1183-3 (by Chapman Bros.)
Giovanni Battista Pittoni The Miracle of the loaves and fishes, 2360-4.
Giambattista Tiepolo Banquet of Cleopatra, 103-4 (by F Pollak)