Eric, both those number 3's are to designate the grade of the gun, grade 3 "DH"

The numeral 2s I inquired about would indicate that these 1942 barrels were a second set and somewhere the original 1935 barrels might exist.

Thank you, Mr. Noble. I see that in the book now.
The possibility of another set of barrels makes sense too, based on all the great feedback I have received from everyone.