Winchester Nickel Steel was sourced from Bethlehem Steel Co.
Report of Heat Treatment of Barrel Steel Rolling, 1902.
http://books.google.com/books?id=YzhUAAAAIAAJ&pg=PA181&lpg

and Midvale Steel Co.
George Madis, The Winchester Book
"Nickel steel barrels for the .32/40 and .38/55 calibers Winchester 1894 were available after 1895 as a special order option. The barrels were stamped M.N.S. (Midvale Nickel Steel)."

I do not know the source for Winchester Standard Ordnance Steel

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