That does not mean that some may not have appeared to have been of stainless-steel construction. Some Hi Powers imported by Browning Arms have sported both electroless-nickle or hard chrome finishes, either of which may be confused with stainless. Electroless-nickle tends to have a slightly yellowish hue to it while hard-chrome does not. It is either white-colored or sometimes appears a very pale light blue.
Several years ago, a company called Baford Arms did produce stainless steel Hi Power style pistols but they have long since gone out of business and there is currently a company in Florida producing both slides and frames of stainless construction. Some aftermarket Hi Power parts have been manufactured in stainless but FN has not manufactured any stainless-steel Hi Powers.
On some auction sites, FN and/or Browning-marked Hi Powers are being advertised as being of stainless steel construction when they simply are not.
Such Hi Powers can indeed be very fine handguns and either electroless-nickle or hard chrome does enhance corrosion-resistance but the pistols are not stainless steel.
(The picture to the right of this article shows a customized Browning Hi Power. It has a hard chrome finish. The S&W N-Frame revolver next to it is of stainless steel construction.)