HELP NEEDED TO IDENTIFY KNIFE

[VANDOO]

I HAVE HAD THIS KNIFE SINCE THE 1960'S BUT HAVEN'T GOT AROUND TO TRYING TO IDENTIFY IT UNTIL NOW. IT HAS A 8 5/8 IN. STEEL BLADE WITH SOME MARKINGS ON IT PERHAPS WRITEING? A 4 6/8 IN. BRASS HANDLE THAT IS HOLLOW SO THE KNIFE HAS GOOD BALANCE BEING JUST A BIT HEAVY TO THE HANDLE. IT IS 13 3/8 IN OVERALL AND HAS A LEATHER SCABBARD.
THE ODD CROSSGAURD LOOKS KIND OF LIKE IT COULD HAVE BEEN USED AS SOME SORT OF BAYONET BUT I HAVEN'T SEEN ANYTHING LIKE IT. ANY INFORMATION OR COMMENTS WOULD BE APPRECIATED.