In the early 1920s American commercial aviation was begging to be regulated by the government! One of the problems of the lack of supervision was that it was difficult to get aircraft insured. The N letter register was set up not by the government but by Underwriters' Laboratories. Less than 50 aircraft were entered in this voluntary register, however. N-ABCC was one of the first. UL suggest the photo was taken in November 1921 when John Yonge, on the right, became the ninth pilot registered by UL. Photo from: UL Solutions