According to the "Lincoln Service Bulletin" of January, 1930 (vol. 7 no. 1) a new steering gear assembly was introduced on the "new models". There were 4 assembly part numbers: L-50642-AR stamped M, L-50642-BR stamped N, L-50642-CR stamped P L-50642-DR stamped Q. All the parts except the housings ( internals, etc.) were the same; the housings had different angles to them to fit different bodies. The worm and rollers were the same for all four assemblies and had a 18 to 1 ratio. Are you a member of the Lincoln Owners Club?