Hello Gordon,
2420905 is the engine number
836409 is the casting number for a 1931:
http://home.znet.com/c1937/Cast.htmB 20 1 is the casting date - Month, Day, Year - B=Feb., 20, 1931
6AE21192 is the car serial number where 6 is the plant code, Oakland, CA. in this case:
http://clubs.hemmings.com/clubsites/chevytalk/GMhistory/1930onplantcodes.htmlAE is the model code for the 1931 passenger, 1/2 ton truck, and sedan delivery
http://chevy.oldcarmanualproject.com/models/series1.htm21192 is the production sequence number.
Happy Motoring,
Dan