We exchanged several emails across the day, and he shared some interesting facts with me regarding Sadler. It seems that this visitor has corresponded closely with Jonathan Pittaway, co-author of "LRDG Rhodesia". I've corresponded with Pittaway as well, and gained some resources in the process.
With luck, this contact will put me closer to finding closure to a number of questions.
I also ran across an Ebay auction for a Howard Sun Compass that offered a copy of azimuth tables that I have been looking for a long time now. Hopefully, I will be able to score a copy of that, even though it only covers 30 deg N to 30 deg S in latitude.
Today's research drifting also came across a posting on Military Photos.net from Kuno Gross. he seems to have come across a working replica of a Bagnold Sun Compass, so now I am on the hunt to see if he has information regarding his source. Hmmm, an interesting day indeed.