I do not know the U-number for this one but I do know that these certainly do not show up very often, especially in nice mottled colors! An intriguing unipart which Joe M and others believe was made by Porcelain Products for the New England Power Company. During the 1980s a number of these were removed from service from 4,160 volt lines in central Massachusetts. Many were rather drab looking. The piece shown has very nice mottling and glaze drips. It's mint except for a mosquito-sized/shaped micro-flake off its outer skirt. As usual, a no-questions-asked refund if you do not like it (shipping expenses excluded). When was the last time you saw one of these for sale? How does $30.00 postpaid sound anywhere in the US? Thanks!