Thanks René! It does indeed look like a Mk V, though the strap looks like it has been modified (i.e. the stitching on one end has been undone and the brass hook removed). I suspect the "VA" refers to the bag being a Mk V (I think the "A" denotes the bags use with the long hose respirators of the navy and air force). The "A/|\N" may very well refer to the Australian Navy.
With all that said, I have to say that the date is the oddest stamping I have ever seen!