It's a copy mate.. Got it about ten years ago I think..Aye Up Caswcc,
How long is ages to you pal? I had one of those back in the early 1980s! (This might be relevant) Rambo film inspired I think.
I've still got the sheath and some of the bits - not the catapult rubbers, like yours they perished.
If yours is the same it will have a small sharpening stone inset on the rear of the sheath and just below that 'pat pending and made in Spain'.
Mine was made by Aitor, I bought it overseas.
Yours does look identical and the dimensions are the same but the business end of the blade looks different so it could be a copy.
Good Luck with it.