NOT a fine double, but for the few still interested, the Winchester Model 37 barrel was marked "Steelbilt". According to Ron Stadt's
Winchester Shotguns and Shotshells the Model 37 series was identified as "Steelbilt" simply because "This new Winchester is made with steel in all metal parts...." by deep draw steel forming. As opposed to a malleable iron frame? Ah marketing
I have not found any statements as to the composition of the barrel steel.
A 1937 ad
https://books.google.com/books?id=7aoTAQAAMAAJ&pg=RA1-PA160&lpg 
