Gray BT-1
The Gray BT-1 built in 1928 was a four place open cockpit biplane. The one built was registered as N2850 but also seen as N2851 c/n 1, which was "a temporary ID issued erroneously," according to a NASM abstract, and which was cancelled in 1929 and replaced by the lower number.
Engine: Hisso I, 150 hp
Wingspan: 37'0"
Length: 18'6"
Seats: 4