This is a close up of the two embossings in this CD. The JM is in a reworked SyM mold. The y does not extend lower than the other letters, the blot out also does not extend 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 does not extend below the other letters, then the insulator is the less pointed domed CD 133.5. or is a CD 133, or is something in between. The other variant has a more pointed dome and I would consider a true CD 133.5. Of the insulators I have found in Mexico, the SyM embossing is much rarer than the JM.