It is in my opinion that when it comes to this kind of situation I like to use just plain common sense. I would think if a manufacturer went through the trouble of either making dies or finding the original dies, and reproducing a quality item, why then after going through all the trouble to make it look as perfect as possible, why then would they not put the spanner pommel nut on top. I have a little bit of a machining background...not too easy to make dies and for sure not cheap, like I said if it were made to deceive that would be a quick give away. Also the spanner nut would be easier to manufacture than a slotted nut.
I'm willing to take this dagger apart to prove any point needed to be made but the wood is a little on the brittle side however it looks just like this one, this one having the spanner nut. Notice how they split the numbers on each side of the crossguard blade hole, mine is also the same way.
http://www.simplydaggers.co.uk/user/image/go2.jpgHere is another one.
http://www.craiggottlieb.com/engine/inspect.asp?Item=2178&Filter=ArchiveRich
