Given the time sequence, the Model 168 was designed circa 1941. This makes it completely impossible for a jet transport to be using that same model number.
Earliest non-flying-boat passenger transports in Martin's design lists are the 24/27-passenger Model 173A/B (circa 1942), and the Model 200 (circa 1943) which preceded the famous 2-O-2 family. But of course these were strictly prop-driven aircraft. First jet passenger transport project was the Model 306 (circa 1956), and even them it was only a twin-jet derivative of the 2-O-2. Only other identified jet passenger transport was an as-yet undesignated derivative of the Canberra, but it was of a much smaller size and could only accomodate 11 passengers. Earliest known jet aircraft design is the Model 218, a twin-jet high altitude fighter (circa 1945).