Rich, I really like your sign, I bet it will look really fantastic once the neon is up and working.... As to a specific Oil Company, sorry I can't help you as, I have no idea....
Looking at the sign, it strikes me more of one that would have been outside one of the hundreds of Independent Trucks Stops along the highways and byways of the 50s and 60s..
But just as easily, it could be tied to a small regional Oil Company, also...
Try contacting Wayne Henderson... Since he has his new book out on All-American Truck Stops, he just might have an answer for you.