they also had to put it thru a series of tests to ensure proper doping of the fabric on the wings upper and lower surfaces per CFR 14:121:87g
Doping! Oh man that brings back memories of when my friends and I restored an old Taylorcraft. Coat after coat after coat, a layer of silver coat, then sand off to smooth and repeat. The factory that sold the dope is now a upscale lawyer’s office, and the one airport we used a giant mall.