Your best possible source for such information may be right here. I've only been in the hobby for 2 years, and between my own postings asking about fakes, and the hundreds of others asking about fakes, you learn a lot right here. It's not hands on but that can only be gotten through shows, flea markets, retail antique stores... it will take time.
One of the first lessons is this, if buying on eBay and it says, India or Argentina or..... Stay away!!
Be cautious as you start out. It's better to error on the side of caution. I remember the first summer I was in this hobby. I was at a large flea market and a guy had a Texaco Lubester plate. I just didn't' know, so I walked. Looking back now I believe it was real and it would have been a good buy. But then, my naive eyes just weren't sure. You don't want to waste money. Be patient. Get some experience.
As for your Esso sign, I have no idea. But that sloppy looking lettering along the bottom screams India to me. But I've never seen an original of this sign so maybe they were like that. I dont know.
Good luck and welcome to Oldgas!!
Always interested in Sunoco items!
Really want a Sunoco National pump add glass!!