The one on the left has an embossed backward 5 on the dome. It is embossed: NEW ENG TEL & TEL / CO. It does have a small glass 'blob' after the C in CO, so perhaps that is an extra period? The one on the right has a dot on the dome, and is embossed: NEW ENG TEL & TEL / CO. This fatter style has a wide mold line. *No, I don't know what that extra embossing is doing on the left insulator. Trick of the light, I'd say! Again these two are EIN [010]