Brand new to the Schwinn Stingray camp

[Sl_y_guy]

So my girl got a Stingray OCC Chopper for next to nothing. She has seen that the rarest ones fetch a pretty penny and has probably the highest expectations but I don't necessarily know what to figure it at. I've checked some sites about serial number locations as opposed to date numbers or however it goes but I really just have no idea about it entirely. My question is what is the absolute 100% way to tell if this bike is one the common ones or not? Or even a good reliable source of info so I can know whether to ditch the whole idea or if it is worth dealing with. I appreciate you guys knowledge and advice for sure. I would include pics and all but It is nothing special right now and I am sure y'all know somewhere or some number I can find easily to see how normal the bike is or isn't. If we get lucky I will definitely get some up. Thank again