Model Variants (Including Prototypes)
RP-1 - Initial company model of 1935
RP-2 - Company model of 1938
RP-3 - Modified RP-2 of 1939
RP-4 - Modified RP-3 of 1939
RP-5 - Company model of 1941
OQ-1 - Initial production version for US Army; 53 units produced.
OQ-2 - Definitive production version based on RP-5 model; nearly 15,000 units produced.
OQ-3 - Improved variant evolved from OQ-2
OQ-14 - Improved variant
TDD-1 - USN designation for OQ-2
TDD-2 - USN designation for OQ-3
TDD-3 - USN designation for OQ-14