NR from the CMPicon forum, maybe the experts are lurking here? I recently obtained a 16 inch bayo (stamped SA, flaming bomb, 1908, US and 267649) off Fleabay. It cost only a C-note and obviously had some rusting, and so I wasn't expecting a stellar example. While indeed it isn't, what arrived is markedly better than what I was anticipating. It has some deeper rust and pitting along the unsharpened edge and at the point, apparently due to condensation or other prolonged water contact. But most of the blade is fairly smooth and clean, seemingly with a patina due to air, not liquid water, oxidation. Most of the metal shows a black, non-pitted surface surrounding a myriad of silver dots. See photos below:





Note that the pics appear to show substantial roughness, but on the contrary the surface is very smooth and the dark areas shown are not depressed (pitted). In the small areas of deeper rusting and subsequent pitting (see the patch at the upper right of the top photo), the surface is all black with no silvery points.

Are there any metallurgists or other knowledgeable types here who might explain this surface? I'm guessing that this blade has had a (unique?) oxidation history that now shows the metallic grain structure at the surface, the silvery grains perhaps containing a bit more chromium and/or nickel than the dark ones. I welcome any informed confirmations or denials!
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