CD 121 AM.TEL.&TEL.CO.  Purchased in March 2011 from a bottle/insulator/antique dealer. He purchased a number of irradiated insulators from a man in Indiana who had access to a food processing radiation unit. The dealer was on his way to California to sell them to collectors who wanted to add 'color' to their collections. I personally saw another Am Tel 121, a CD 145 'B', a CD 145 N.E.G.M.Co., and a CD 205 Gaynor that were all a similar inky saphire color. He also had a brownish amber diamond pony and CD 232 Hemingray that had been altered. None of them were marked. I purchased this one because of the purple undertones and unbelievable uniformity of color throughout. Too bad none were ever produced in this color. According to the dealer, this is the last lot that the individual is going to irradiate. Apparently, it has become cost prohibitive.