These old Tel Fed Mex insulators are interesting. An old style with an odd embossing, and great color. I have most of the known embossings and shapes to compare. If I can get the pictures downloaded properly, the first picture shows all of the shapes and embossings. At the left is the CD 133 TEL FED MEX with JM on the back. On the far right is the CD 133.5 TEL FED MEX with SyM on the back and then the same insulator in the reworked mold with JM on the back. On this shape the leg of the y extends lower than the other letters so the blot out also extends lower. If you look close, you can just see the blot out. The center two are the odd CD, not fat enough for a CD 133, and not as pointy domed as a CD 133.5. On these the y in SyM does not extend below the other letters so the blot out in the reworked mold is also higher. Hopefully the difference shows up in the next two pictures. The blotted out S shows up as two small blots, one above the other. The J is over the blotted out y.