STETTINER OELKONTOR K. MATTERN.
image by Klaus-Michael Schneider, 14 April 2009
The flag is a red pennant with a white disc containing black SOK. Black lines edged white run from the corners towards the disc. Rosanoski says the letters should be enclosed by a thick black ring on the white disc. A further website image, apparently derived from Esso, thins the black lines and the funnel lettering.