I never claimed to be an expert, but here’s my take: Yours could very well be a gift engraved to the actor Paul Hogan by his crew. That said, I’m not sure what value a no-brand lockback knife engraved as a gift to Paul Hogan is worth in today’s market, but I highly doubt it was a prototype or one-off model of anything, just a big, generic lockback folder that was probably widely available (and fitting because his character notoriously used big knives), and engraved. It also doesn’t mean he ever personally owned, handled, or even received it. I will say It would be a very strange thing to hoax (maybe less weird in what, 1989, at the height of his popularity?).
Additionally, it doesn’t mean it’s the same knife, or even brand/model used in the movie, which I thought was what the OP was asking some 15 years ago, when you might still have been able to rent the movie at Blockbuster, but, heck, maybe it is.