Andreas: Thanks for the reference to German cross-guards. That's new to me. Wonder what they looked like. The 1871 date could help date some earlier swords that we now have to guess about.
Wisram: great photos of the cross-guard. I'd call it the chisel form favored from Sennar. Not that it was made there, but likely. Could be fairly old.
Picture of the Funj sultan with kaskara sword from 1821 at the link below. The scabbard has a profile similar to yours.
http://en.wikipedia.org/wiki/Sennar_...ennar_1821.jpg
Here's a possible scenario for the history of your sword. Blade imported into Abyssinia in mid-19 century and made into a sword of the local style. In March 1889 there was a big battle at Gallabat/Metemma between Mahdist forces (85k force) vs. Abyssinian Emperor Yohannes IV (130k force). Mahdist forces won and Yohannes killed. Along with Yohannes' head, your sword was taken as a war trophy. Sword was taken to Sennar, maybe 90 miles away from the battlefield and put into kaskara dress along with Sennar style cross guard. The silver grip is top quality, but the sword has been used over time.
In 1940/41 British and Italian forces clashed in the Gallatbat border area, and the reported (British soldier ?) got the sword in the Sennar area and brought it back to the UK.
Top shelf sword.
Ed