20W50 Castrol GTX...was in the 1/2 and full litre glass bottles in the racks at the service stations.
Oft next to the "store brand" bottles, you could tell the GTX as it was a greeny tinge, not brown/yellow.
1987, when I worked in a service station, there were two full racks of GTX glass bottles and pourer/lids...boss told me to take them to the dump, or take them home...I took them to the dump.