A gentleman selling older rifles at a recent gun show told me that the metal finish on early Springfield's including Krags was basically a coating from oil in the quenching process that wore away fairly quickly.  In other works, there was no chemical reaction as with various bluing processes.  He said the mottled black appearance so common in older firearms was simply remaining areas of this coating.  I have a rebarrelled Model 1896 with a really nice even finish all over.  Per this gentleman, virtually any rifle looking like mine has been blued in some timeframe after it was originally made.  Is this correct?