This somewhat unassuming, censored(blue cachet most likely applied in Mombassa, BEA, or Cape Town, SA), WW1 cover(slightly-reduced envelope is pretty clean, but has wear and tear around its edges in the form of creases, nicks, and tears(mostly at the right side connected to the initial opening of the mail)); back flap is 90-95% intact) has a fascinating(never seen another item like it in my 45 years of collecting!) history behind it! It was sent some time in late September or early October 1917, by American missionary, Reverend Harry H. Hurlburt(name at the right side!), from Aru(near the border of present-day Uganda), Belgian Congo, to a Mr. Robert M. Ford(possibly a supporter of the sender's missions work?!), Los Angeles, U.S.A.! On its way from Aru, it went through Port Pawa(?), Belgian Congo(?), across Lake Albert, to Butiaba, British Uganda Protectorate, and then onto Mombassa, British East Africa! From there, the mail was sent onto Cape Town, British South Africa, where the blue, 2.5d South African stamp(in fair condition at best due to the damage at its top, right corner that incurred before it was put on the mail) was likely applied and cancelled with a great machine cancel on 10/17/1917! It's impossible to say when this mail would have reached the addressee, as there's no receiving cancel from any U.S. post office. Noted imperfections aside, this cover remains a rare, extraordinary piece of WW1-period mail from an American missionary in Belgian Congo that took an amazing journey through war-torn East Africa to Los Angeles, U.S.A.!