As you can see, this is half of an insulator. CD 238.2 Armstrong insulators exist with two different style heads- one identical to a CD 230.2 51C1A, the other slightly different (larger). One complete example of each version has been found to date, and this half is one of two currently in existence. It features the 51C1A style head. To sum up, two complete, and two halves in existence. This is probably a once-in-a-lifetime opportunity to acquire this highly elusive CD. There are no markings on this insulator, but I will provide appropriate documentation to the purchaser. $815 postpaid.