Australian Dept of Defence D/l\D on the receiver
 

I have a 1914 Erfurt Artillery luger which has the Australian WW2 D/l\D mark stamped on the receiver.
This would indicate it could have been issued to an Australian unit in WW2.
Whilst there are a few pictures of Officers with lugers and unit diaries show requests for lugers as a side arm (in particular independent companies, the predecessors of a Commando unit) destined for the Pacific theater, I have not seen any primary evidence for them being formally issued.
Appreciate any information.
The logic was that using the luger as the standard side arm in place of the 38 revolver would mean one less type of small arms ammunition was needed.

Not sure of that logic, 9mm was not a common round outside Europe. Japanese did not use it.
Other than the Sten, the British did not use it. The Sten was because they were for use by Resistance and the 9mm WAS the available round in Europe.
More like a capture from WWI when Australia annexed New Guinea to deny German raiders a base.
Look up the SMS Emden

Don't forget the Dutch East Indies Army was just around the corner and many evacuated via Australia when they were overrun by the Japanese.

Although the Dutch used the M11 (1906 style) and the navy used the Model 1 (P08 style), many other guns were in use there, including C96 and former WW1 LP08 and P08 pistols.

So it is not impossible that this example wandered into Australia during a WW2 Dutch retreat.

Australia was desperately short of weapons at the start of the war and issued a directive for any firearms to be "donated" to the government for the defense of Australia.

If that marking is authentic the pistol is possibly a WWI bring back that was turned in when WWII began.
It could have been inventoried and issued to a home guard or similar unit early in the war.
It's possible it was carried in combat by an Australian soldier but more likely it never left the country.

The Brits used 9x19mm in the Inglis Hi-Power and Sten. Australians used 9x19mm in a number of firearms including the Sten, Inglis Hi-Power pistol and Owens Gun. 9mm was well know outside of Europe long before WW2 erupted.