I have just been allowed to touch and feel a set of "Superfine Knitting Needles" made by THOs Harper & Sons', Redditch England full set No. 17. While I have looked at them with a hand lens, I have not fully characterized them yet. The are basically 1 mm steel lace needles, about 8" long. They have significant wear, but I do not see the wear marks of a knitting sheath on them.
They are mild steel, tempered for springiness. This tells me that old needles were spring tempered steel - even when they were not being used with a knitting sheath/ knitting pouch. But no, I do not yet have a statistically significant basis for that theory.
They are very like the superfine steel needles that I make, and very unlike the steel needles that I have recently purchased through commercial sources.
Aaron