09/30/2016. Remarks by Johan Visschedijk: "Three DH-4M-1s were fitted with new Boeing designed tail planes, tapered wings, and tripod landing gears and were given the new Army designation of XCO-7 for Experimental Corps Observation Model 7. This was an attempt to extend the service life of the basic DH-4 model and make further use of the large quantity of de Havilland equipment that was on hand.

XCO-7. The first XCO-7 (serial 22884 c/n 520) did not fly, being used for static tests.
XCO-7A. The second was designated XCO-7A (serial 23109 c/n 519) and used a completely standard DH-4M-1 fuselage and Liberty engine installation with the Boeing modifications.
XCO-7B. The third was designated XCO-7B (serial 31216 c/n 521) and differed from the A in having balanced elevators and an inverted Liberty engine that the Army had been developing. Both flyable XCO-7s were shipped to McCook Field, where the first flight was made on February 6, 1925.

The performance increase did not justify the cost, and the Army turned to entirely new designs."