These are the two types of A.B. Chance 25kV line posts used on the Tillamook, OR. PUD system. The brown one on the left is likely pre-1966, since it is brown. The sky-blue one on the right says '1969 Chance 2000' and because of that, I don't know which year it was made. It is heavier and a little larger than the brown version and has 'Type F Neck' written under glaze on the top. There are no 'U Numbers' for line posts, BTW!