I worked in A real Philips 66 service station( That was when "service"
meant filing your car with gas,checking the oil and tires and washing
all your glass! Now service is selling lottery tickets and milk) as a
pump jockey in the mid 60's and one of my jobs in the morning was to
fill those jars and put them in wire racks with the little sign on them
telling the other guys if they were detergent or non-detergent, what
weight they were and the brand. We sold Philips oil in 4 types and 6
weights and Pennzoil in at least 6 weights.
I was glad when we went to all canned oil in the early 70's.
I worked there full or part time for 16 years working my way up to
mechanic.

Good Luck!
H.R.