Shotgun!

I am trying to find information on a shotgun I inherited from my maternal grandfather. It's a neat little 20 Gauge pump, a Ward's Western Field Model 60-SB620A. They were made from 1930 up into the Forties, IIRC. I can't find a serial number, so I suspect it was made before the 1934 Gun Control Act.

I need a manual (file okay) info on how to date it and so forth.