Richfield sign 72"

My father owned an auto repair shop in the 50s & 60s and this sign is from it. I came across it in storage the other day and figured I'd see what info I could find online about it. My dad died when I was a kid and I have no one else to ask about it. It's 6ft wide. Metal with porcelain enamel maybe? One side shows more wear than the other, as you can see from the photos. From what little info I could find online, it looks like there were several versions of it. Different sizes and different products like octane, for example?
Thanks in advance for any info. I appreciate it.