Continuing research often closes some doors and opens others. That's the fun of our field. The blade soat'al form has lasted a considerable period. But the grip/handle has evolved and perhaps the back-to-back "C" configuration was a modern innovation, perhaps at the time of the Eastern Camel Corps participation in the 1916 Ali Dinar Campaign, perhaps even later. It would be interesting to see soat'als from various periods.
The C grip is held by the first and second fingers which allows better range of slashing motions than a conventional "fist" grip. See the post and period photographs below. Note that most of the Beja wear the old J shaped blade knife with its characteristic fist grip.
http://www.vikingsword.com/vb/showthread.php?t=9991
Ed