This is a CD 728 threadless in nice aqua-blue which was found on the Central of Georgia Railway telegraph line. I believe that this was the most common style of threadless - at least I found more of these than any other style. I found maybe four or five and they were distributed South from Macon to Albany, GA and North from Macon to Griffin, GA. I found more on the line North of Macon. In general, the line North carried many more older "signal" styles. I have two different color variations in my collection, but this one is the closest to mint and has some amber swirls for character.