Here is a close up of what I would consider an embossing error. To me the PO of POSTAL is a smaller lettering set then STAL. Not to mention that the S is upside down. However that seems the norm for the CD 138's with the smaller embossing. Both my smaller embossing type CD 138's have the same S. Contact me if you agree or disagree as to whether or not the insulator in question is an error or if you also have one like mine.