The number 940 makes me wonder if it's a larger version of the Large Frame which was used to make 12 & 16ga. shotguns. The 9-- series of numbers ends with 938 so it seems logical to assume the 940 was a larger frame for 10 & 8ga. guns. Frank de Haas goes into pretty great lengths to describe the guns in "Single Shot Rifles and Actions", copyrighted in 1969 and published by DBI.

Don't know whether or not I'm correct in this but it seems a good start.