Looks like its part # 679888 which is the part # for a 1938 P5,P6,D8 &D9 transmission case. Casting #'s are typically 1 digit off the part # on a lot of mechanical parts. I have a copy of the 1938 parts book dated Nov 1 ,1938. It's a Canadian book...# WM-3561. The 4-7 is a date code...possibly 4th quarter 1937...maybe 4th month 1937 .