This highly unusual Navigadget Mark I Flight Computer is the first and only one of its kind that we've run across.
Measuring 10 x 5.25 inches and painted on aluminum, this device seem intended to be placed on a chart with a scale of 1.25 inches = 10 miles, with the left "Miles" scale placed along the intended flight path. The center axis intersecting at the 40 Mile-mark is the calculated ground speed, from 60 to 150 MPH.
The aluminum semi-circle plate in the center is marked in minutes. By putting its first "0" on the angled line marked "Start" which leads to the "0" on the Miles scale, and slide that semi-circle edge over to 60MPH, any angled line from the Miles scale lines up with the number of minutes it will take to reach that mile total traveling at 60 MPH. At the 60 Mile mark, the angled line to the semi-circle lands at the second "0", i.e., 1 hour later.
At the bottom are two graphs - the one on the left shows the reduction of air speed at various wind speeds. The graph on the right computes the required course correction at various wind directions and air/wind speeds.
At the top is a rotating compass rose to compute the required magnetic compass heading deviation to remain on course given wind direction.
On the reverse side, a previous owner has marked it "WWII 8th Air Force B-17....". We have found no evidence that supports this marking, have not found any references to this device in any US military manuals before, during, or after WWII, and do not see any formal labels on the device that would indicate that it was a tool sanctioned for use by US military aviators.
We believe that it was intended for use by an air navigator/observer or as a training aide by a student pilot. Given the air speed markings, it was not intended for use in an aircraft capable of air speed in excess of 150MPH.
A cool little aviation gadget, regardless.