I think Derek and certainly Ron can add much more than I on these, but Jeffy
has really done some outstanding research on these blades, and most of the data I have has been acquired from his posts.
It seems plausible that the blades may have been supplied to Abyssinia via British exporters during the latter 19th century, despite thier Solingen production. Apparantly the Abyssinians particularly favored British products and Mole as well as Wilkinson furnished blades during this time. Wilkinson did not dominate the furnishing of such blades until the early 20th century,and by 1932 they appear to have exclusively furnished blades for the Ethiopian government under Emperor Haile Sellasie. Great Britain occupied the Port of Aden in Saudi Arabia, which may have been a source for the German blades as it was a key trade center as well. It would be difficult to determine more exactly, giving the political volatility prior to, during and just after WWI.
Many of these weapons may have seen service during the campaigns during the occupation there by Italy into the 1930's, however most seem to have been parade or ceremonial weapons. Most narratives, or historical accounts of these times and events typically carry little detail on weapons, however they do provide a good perspective on the costume and uniforms worn (especially "The Italian Invasion of Abyssinia", David Nicolle, Osprey #309).
Best regards,
Jim