Found it on p.109 of Charlie Pate's book "U.S. Handguns of World War II--The Secondary Pistols and Revolvers."
It says...
"Many Australian arms have been noted with the Broad Arrow having various letters on one or both sides of the arrow, for example - "A (arrow) F" or "D (arrow)" or "D (arrow) D". Variations are also reported having the D over the Broad Arrow and the Broad Arrow within a D. The "A (arrow) F" has been reported to be the property mark of the Royal Australian Air Force; however, other credible sources state this mark is simply another variation also meaning Australian Forces."
HTH