This post compares the back of a SCA CD 133.1 Dec 19 1871, Electrical Supply Co Chicago, and a Patent Applied For telegraph bullet. The first two were found between 1973 and 1975 on the Chicago Northwestern Railroad as it ran East out of Boone, Iowa toward Ames, Iowa. The CD 133.1 Patent Applied For was found on the Central of Georgia Railway in Georgia. Details on these insulators are as follows:

CD-133.1 Patent / Dec 19 1871 (Front Skirt) - 3 /A (Back Skirt Mold Style Number & Letter - Light SCA (Microbubbles & Cull Stones) - Measurements: 64 mm Wide x 89 mm Height. (Light Embossing) [click here] (Pictured On Left) [id=614294556]

CD-133.1 The Electrical Supply Co /Chicago (Front Skirt) - 25 (Top Dome Mold Number) (No Embossing On The Back) - Yellow Green (Microbubbles) - Measurements: 64 mm Wide x 89 mm Height. [id=614293547] (Pictured In Middle)

CD 133.1 Pat App For. (Front Skirt) Large Script 3 (Back Skirt) - Crude Brookes Blue With Bubbles - Measures 73mm Wide x 103 mm Height [click here] . (Pictured On Right) [id=603665927]