Weston Aircraft Instruments

Aviation Yearbook February 1942 McGraw-Hill

Part of the Weston Electrical instruments company founded by Edward Weston in 1888. History here. The Duke also did an earlier post on a voltmeter made by the company here.
 I find the use of the Liberator in the ad interesting and a bit optimistic. The ad dates from February 1942, so the US had barely entered the war as the magazine was being composed. The first Liberators had only entered service (with both the RAF and the US) in mid 1941 and there might have been only three dozen flying at the time this was published.