Waco YKS-7

The Waco YKS-7 is a fully enclosed cabin biplane, configured with two front seats and a rear, bench seat for three more passengers. The engine is a 7-cylinder, 225 hp Jacobs L-4 radial engine. Its cruise speed was about 130 mph, with a range over 500 miles. Compared to automobile travel in 1937, the Waco YKS-7 seemed like a rocket ship.[Source]

Notice the registration, or N-number. Aircraft registered in the US still begin with the letter "N" to this day. The second letter, "C", signified that this airplane was for commercial use. ("P" for private and "S" for state-owned were the other options.) The second letter prefix was dropped in 1948.