There is good info.here on decoding sealed beam headlamps pluse other interesting info,its in a PDF format & I don't know how to post a proper link sorry if it is of no use or maybe someone can properly post a link. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&cad=rja&uact=8&ved=0ahUKEwiOm43tv5rbAhUQyFkKHfbRC78QFghXMAk&url=https%3A%2F%2Fwww.gpo.gov%2Ffdsys%2Fpkg%2FGOVPUB-C13-722c70411c03edd33c762f29d5948ff6%2Fpdf%2FGOVPUB-C13-722c70411c03edd33c762f29d5948ff6.pdf&usg=AOvVaw3DM5fjvp6OqxSVVeSjaUby