Iain/Colin,
I've done subsequent research on the origin of the Hadendowa soat'al and it seems that the 1916 attribution is apocryphal. I inquired to the British Badge Forum that showed a badge of the camel corps out of Eastern Sudan. See attached link to the link. Eddie Parks of the forum informed me that a very similar knife to the soat'al had been collected in 1882-83 by Juan Maria Schuver before his death in Sudan in 1883. Unfortunately, the link provided is no longer active. Perhaps others can penetrate the Schuver Collection in the Rijksmuseum Volkenkunde ( National Ethnographic Museum) in Leiden for the image. Its very close in style to the lower knife Colin posted. Very likely the Mahdist period attribution is correct. Note that Colin's grip form is more Nile Valley as opposed to the more emerging "modern" style of Kassala suggested on Schuver's piece. Both blades are pretty much the same.
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http://www.britishbadgeforum.com/for...ad.php?t=25756
Link about Schuver and his travels.
http://volkenkunde.nl/sites/default/...schuver_uk.pdf
Below is a scanned fuzzy image of the Schuver's 1882-83 collection piece.
Regards,
Ed