Weather Bureau Winds Aloft Plotting Board
This plotting board is pattern used by the US Department of Commerce, Weather Bureau for determining winds aloft from pilot balloon ascents. It measures 36"x36" and is quite heavy. There are six different distance scales (and related velocity scales) on this board. It lacks the printed instructions for use that the USN pattern boards have, although it is used the same way. Meteorologists using board presumably were familiar with its operation or used accompanying texts.
