This is only a guess but the 2 finger symbol was to remind you to change your oil every 2,000 miles which was the practice at that time. As longer life oil & engine improvements came that changed.

Kendall also avertised themselves as the "asked for motor oil".
Many gasoline brands didn't allow there dealers to have other brands of oil on the island display rack. So a customer would have to ask for Kendall which the dealer had to keep inside the station.

Dave