Well there are men who fought in WWII that enlisted before WWII (before 1939 & Dec 7th 1941). The name "Jack" can be used for the name "John", Remember John F. Kennedy was also called Jack Kennedy. Ancestry and Fold3 have Military databases but if you just have the name and in Melbourne with the 1st Marine Division then will be near impossible to identify the correct one. A rate or Rank, "job" in Division and there are also Naval personnel that were part of support (supply, mobilization) units of Marine Companies. Also having the state where lived before war or enlisted in would be a help.
In Ancestry's military databases there are 4 men named Jack Rice that were KIA for WWII. There are at least 8 men maned Jack Rice in Marine Enlistment Rolls before the year 1945.