Question where to use the magnums safe key

[maurice br]

i dont know if i missed it because it whent to fast but at the end of the dont drink the batwater quest i looted magnum's safe key but never found the bloody safe also cant find one reference in the diary could be that the trunk was marked as safe so but u cant check that ones the lock is opened !

 

[kinggath]

The safe should be on the level just below Magnum, though I don't recall specifically where it is.