So the seller of the unit on eBay indicated that the only numbers on this "sextant" are:
206C-145
Well, it turns out that this Brandis is an interesting and somewhat unusual instrument. Something about it just didn't seem right and it took me a while to figure it out. All the sextants we've seen up to now were held in the right hand and sighted through the tube mounted the right side (when viewed handle side down). This one is to be held in the left hand and sited through the tube from the left. When I studied the grip, I realized it was designed to be held in the left hand. In addition, the arc was much smaller than sextants we've looked at, and it has various wires indicating that it utilized a light of some sort.
What we have here is a left handed Brandis aeronautical octant.
According to this website:
https://sextantbook.com/category/unusual-left-handed-sextant/it is a model 206C, serial number 145 out of an estimated total of about 200 units made. This one is missing the bubble telescope, and what we see is the sighting tube. It is also missing the legs that allow it to be set down with the handle side up.
The same website dates #125 to 1931, so presumably #145 is somewhat later in date.
Compare the photos attached. The third photo shows a right handed Brandis sextant with the bubble telescope for comparison.
Doesn't really help us move the thread forward, but it is interesting to me that new information about the Brandis product line (and Amelia's flight in general) keeps popping up.
Andrew