Here is a marked U-864 Blue Locke. These are really cool! Note the similarity in glaze color to the blue Locke U-866 in the previous photos. I discussed blue glaze color in the U-8xx group of power insulators with blue porcelain expert Jimmy Burns and found that glaze color has to be ruled out as an identification point in this group, since several manufacturers, including JD, Locke, Pinco and Westinghouse made many blue glaze variations that were identical.