Thanks, Flying10uk, I did use the wrong terminology (I'm not a bayonet guy). It is indeed a non-hooked cross guard, not a quillion. It appears to me that the blade has a blued section as you describe at its base and the rest was originally in the white, now stained and spotted, but with very little pitting.

I've used oil and bronze wool on the non-blued section, which lightened some of the heavier staining but left most of the discoloration still there. This type and amount of staining would almost without exception result in pitting on a Japaneseicon sword, with which I'm more familiar, so I find it interesting that there is next to none here, save one formerly crusty patch towards the tip.

I'm wondering whether perhaps naval jelly, vinegar or the like would leave the blade looking near original, save perhaps a slightly frosty appearance. I'll try to post some pics as the blade is now, but need to wait for daylight tomorrow.

Thanks again to all for your responses.