These are of the so-called Commando/Ranger WWII Knuckle-Knife style in that they
are crudely made - as if individually from a garage or workshop bench - hence "benchmade";
they ususally emply a large brass or aluminum "knuckle-guard" and a large "bowie"
There are quite a number of variants and I would venture to guess that most examples
on the market today are spurious, although legitimate examples are known. I would
recommend study of M.H. Coles' books on Military Fighting Knives and Ron Flook's
book on British and Commomwealth Military Knives.
If you need further information concerning markings or blades, please post your questions to me directly via E-mail.