"SOC" on the truck of "Last Lord of El Dorado"

[lgiver@postoffice.pacbell.net]

I just re-read Don Rosa's "Last Lord of El Dorado".  Cataract
surgery last month has improved my vision, so I could use
my "eye for detail" reading this story.  There's an interesting
design and the letters "SOC" on the truck doors, most
readily seen in panel 2, page 14.  The design seems to show
several mountain peaks with 3 oil drilling rigs on them, with
the letters "SOC" (one letter on each rig).  Do the letters
stand for "Scrooge Oil Company"?  Usually the name
"McDuck" is part of a company name, not "Scrooge".
So I'm probably guessing wrong.  What do these letters and
design mean?  
                            Best wishes,    Larry Giver.