Here's a pic from my archives of an altered CD 151. The note passed along to me with the pic states that it was originally a common light blue shade before it was subjected to radiation and thermal exposures. Referencing the recent sale of a similar example on eBay, can these really be worth $1,400+ ????
For more information on identifying altered insulators, please go to: http://www.nia.org/altered/index.htm