You got yourself a beautiful knife, there, Olskool.
To me, it looks like a late 20th - early 21st century replica of an old-time rifleman's knife. There are some craftsmen "out there," including some who frequent this board, who make beautiful reproductions of very old artifacts. Some of these same fellows are also very good at giving those artifacts the appearance of great age. There was some musing on the ethics of this practice on the Contemporary Makers blogspot a while back, right here:
Aging Contemporary Guns
I think there may have been a discussion on the ALR Forum, too, but I'm not sure of that.
I make some knives now and then, using commercially available blade blanks. I try to give the blades some patina in order to give them character and the appearance of having some history of use. I'm not trying to fool anybody and would never present them as anything other than what they are: New knives that are made to look like old ones.
I have warily bought a few things from online auctions, and gotten a couple of bargains and I paid more than I should a couple of times. I think some of the sellers don't really know what they have, and unfortunately I have seen a couple of things for sale that were obviously not what they were represented to be. The old saying, "Let the buyer beware," has never been more true.
Anyway, I think you have a very nicely made but relatively new knife. One like that, with a well finished blade, an antler haft and a neatly fitted cross guard from a custom builder might cost anywhere from a couple hundred dollars to over a thousand, depending on who the builder is. Reselling the knife, you would be lucky to get the merest fraction of that, unless you could verify that it was made by a famous cutler, and it is in pristine condition.
I'll reiterate, you have a nice knife, and I sincerely hope you enjoy having and using it!
Best regards,
Notchy Bob