[mrerick]

Eric, you also asked about detecting re-bluing...

The processes of bluing involve preparing the steel surface, oxidizing the surface and then "carding" or polishing the surface to become more smooth and bright.

The oxides created by the various bluing processes (slow rusting in a humid atmosphere; fast salt chemical change) are black in color. Other forms of iron oxide are red in color (the common rust we see on things left out in the moisture over time). There is always moisture in the air, and red oxide forms slowly over the years even on steel surfaces that have been blued.

An original bluing will be under the control of the single gun maker. The color tone of the blued steel will be more consistent in it's original finish. (There are, of course, inconsistencies when military demand made the factory hurry up, especially on salt chemically blued guns). The metal edges will be sharp and not carded and polished away on an original finish. In rust blued guns, there will be surfaces left in the white without any bluing (some of the pins and the interior rails on a rust blued Luger are typically in the white, as is the muzzle).

It took a great deal of skill to card and polish the blued surface of a firearm properly. These were among the highest skilled (and likely paid) positions in the manufacturing process.

So, an original gun will have more uniform appearance; sharp surfaces and a mix of black and red oxide visible deeply in the surface reflecting the age of the gun since finishing. Areas that should be in the white will be.

Marc