Mike,
I think what you have there is a Moroccan s'boula, likely from Atlas regions of Morocco. These long thin blades, as you have noted, were keenly favored by Berbers in Saharan regions. The opposed carrying rings in baldric fashion are the same as present on the well known koummya daggers also of these regions.
In viewing caravan routes mapped through the Sahara, it is not difficult to imagine the diffusion of these weapons to the south and east where local versions might be fashioned, although with same general characteristics.
Still uncertain of the scabbard/hilt motif, which tribal group may have favored this decoration, but still favor the Mossi by the blade geometric decoration for Tims example.
How could you own this for three years before ID ? I'd go nuts with curiosity !!
. Your example is one of the nicer ones with the engraved handle.
Thanks for posting this!
All the best,
Jim