All I know is from a 21 February 1949 BuAer memorandum: "The Martin design was the carrier landing version of their Model 245, submitted in the 'Special Attack' design competition. No attempt was made to meet the specification requirements in regard to number of men in a crew, access to bomb bay, protected fuel tankage, folding wings, or provision of a turret. Incorporation of these items would increase the gross weight well beyond the specified 100,00 lb maximum." This, combined with the very limited attempt to meet the requirements, suggests that the Navy memo is describing the 245A. A 246 is listed in Martin records but I haven't seen anything that describes it, the time period it was created, or the requirement that it was created for.