Winchester had two proofs, a Viewed Proof (VP)where an inspector viewed the barrel and found no defects, and there was a Winchester Proof (WP)where the action was worked for function, it was inspected for fit & finish and then test fired.
Winchester did take sample barrels and load them up for failure.
Don't think it was "Nitro Proofed". If the finish on the frame is its original finish CCH, which looks to me like it is, then the rifle was MFG prior to 1903 when Winchester stopped case hardening frames.
Winchester also considered the 32-40 a Black Power ctg, and made very few 32-40 barrels in their "Smokeless" or Nickle steels.
The only barrels that I have found where Winchester consistently used Nickle steel in their BP ctg were the rapid taper Extra Light "Pencil" barrels. Not a whole lot of metal there. Believe it was supplied by the Midvale Steel Co. and will have a mark on the bottom of the barrel, M.N.S.
V/R
Mike
