the old 'dark rust blued' finish, however there is no definitive rationale to support that theory as this pistol is in immaculate, like new condition and if they were going to use this as a test piece (for finish durability) usually they are in terrible condition. It has also been theorized that this might have been the very first pistol that was produced with the new 'dark salt blued' finish, vs. In the manufacturing world this would typically signify an early prototype or preproduction test pistol. Obviously the first and most distinguishing aspect of this pistol as noted is the serial number, which is '00000'. This pistol is certainly an enigma within the collector field for those of us that collect Polish VIS or Nazi Radom Pistols.