Unidentified markings on Morse code buzzer signal training set

This is an Australian Army WW2 Morse code practice or training set with Morse key and buzzer. The clip holds a dry cell battery of 4.5V
So far I and many others have been unable to identify P4MOG.
Is it a code for a manufacturer in Sydney?
It remains a mystery so far. Perhaps you can help.
Thank you,
Herman Willemsen
collector of Morse code keys.
former Marine Radio Operator.
Amateur radio callsign VK2IXV