sac troop,
You might be correct about the phosphate. LAst week, I just picked up two 1973 vintage 499s at an estate sale.
They had the exact same metal surface finish as JohnnyB's knife. There are several types of phosphates (zinc, manganese) that are/were specified by the government. I really haven't studied the long term wear look of either. However, the smoother the phosphate surface becomes, the less corrosion resistance is present. So while it may look nicer, it will be more prone to rusting.
Hope this helps.
Best Regards,
Paul Tsujimoto
V.P. of engineering
Ontario Knife Company