Complex sentence: The prototype was designated XNBS-3 (prototype night bomber short distance) and tested by the Army Air Corps in 1924 at McCook Field, it was similar to the earlier Martin NBS-1 and was no real improvement so was not ordered into production.
Split into simpler sentences: The prototype was designated XNBS-3 (prototype night bomber short distance) and tested by the Army Air Corps in 1924 at McCook Field. It was similar to the earlier Martin NBS-1 and was no real improvement, so it was not ordered into production.