Photo found on the Rembering Anzacs website.
Enlistment records when he enlisted as Annesley Alexander William Robert Bede Gamble
Records from Enlistment as Robert Alexander Gamble
It would seem that between deserting on 20th December 1915 and re-enlisting on the 25th September 1916 under another name he also got a tattoo done on his forearm.
notice the above is witnessed by his cousin Mona Hokin.
The above shows that he might have finally been found out after his death by the army for his earlier enlistment and desertion.