Congratulations Rob,
You are essentially correct so I give you full credit for your quick, but not record reply to these quizzes. Your Juptner reference which I also have shows the Approved Type Certificate designation for an aircraft initially revived by the Langley Aircraft Corporation of Port Washington, NY in 1942 that was never produced.
Let's back up a bit in history by way of full explanation. Langley built two prototypes of a twin engine aircraft using plastic-reinforced molded construction, the first of which was the Model 29-65 with two Franklin AC engines of 65 Hp each. My other reference shows first flight of the 29-65 in 1941, not 1940. The second prototype with more needed power was the Model 29-90 with two Franklin 4AC-199-E4 90 Hp engines after initially trying two 75 Hp engines.
The Andover Kent Aviation Co. of New Brunswick, NJ obtained a production license from Langley Aircraft Corporation, but no production ensued because of the advent of World war II. They improved the design and obtained the Approved Type Certificate #755, granted 12-29-1943; prior aircraft were registered Experimental NX.
Langley Aviation Corp. of New York City then revived the prototype in 1946, re-designating it Model 2-4-90 TWIN FOUR, but no production ensued. (Juptner writes "it is estimated that 3 examples might have been built"). The prototype was still in registration by 1965 as N5170S or N51706. I have not checked these numbers for any registration currency as I write this. Juptner shows the prototype Langley 2-4-90 with NX29099 registration.
The Langley 2-4 TWIN FOUR was a streamlined design four-seat cabin monoplane with wrap-around windscreen and with fully-cowled engines faired into a low wing, twin tail taildragger with streamlined wheel pants on fixed gear. Props were fixed-pitch. The wings were tapered into the fuselage at their roots. Think a shrunk-down Beech 18 for similarity, especially in the rear cabin/tail area on side view. The aircraft could fly with one engine shut down.
Performance:
Max speed: 138 mph
Cruise speed: 117 mph
Initial climb rate: 695 ft/min.
Range; 350 miles
Weights
Empty: 1,738 lbs
Gross: 2,850 lbs
Dimensions:
Wingspan: 35'0"
Length: 20'6"
height: 7'1"
Again, congratulations on your quick response.