This is a close up of the two embossings in this CD. The JM is in a reworked SyM mold. The y extends lower than the other letters, the blot out also extends lower. The J is embossed over the blotted out letter y. The S is blotted out with two small circles, one on top of the other. If the y or blot out extends below the other letters, then the insulator is the most pointed domed CD 133.5. The other variant has a less pointed dome. Of the insulators I have found in Mexico, the SyM embossing is much rarer than the JM.