Saka (?), Kusu (?) knife for pleasure and maybe comments

[Martin Lubojacky]

I bought it on eBay last year and I post it just for pleasure here now. The dimensions are: length 48 cms, max. width 14 cms. It was discussed by forumites before - I think it is Saka or Kusu (?)
I like curvature of the blade - without any mistake for me.
But still - maybe a few questions: I did not clean it yet - I always hasitate (as far as African armas are concerned), if to clean the iron fully (BTW as we can see it in most of museums), or to leave it "black" and to smooth it out only.
Was it really "only" ceremonial weapon ? (the blade is sharp, made of hard and springy steel (clangs nicely)
How old could it be ?
Some time ago I heard that this daggers were copied for tourists and collectors very often. Is this one such copy or real item made for "tribal use"? (patina on handle is very nice, but this is not difficult to imitate).
Regards
Martin