I've actually had this mag in my hand twice in my life (the cover gives it away).
Popsci Shell quiz from 1976
Has temperature charts for the grades, and an explanation of which grades were "multi",and which were "mono" grades back in the day.
Popsci Shell quiz from 1976
Has temperature charts for the grades, and an explanation of which grades were "multi",and which were "mono" grades back in the day.