Is this silicone case real or fake ?
iPhone 7
You could try & contact Apple Legal via this avenue to report suspected
counterfeit products or accessories; there also is an official means to
ask how you find out. I'm not looking it up. A search (duckduckgo)
could provide some site links; look into Apple.com support sites.
If you would like to report counterfeit or knockoff Apple products... Which Apple
product is the most similar to the counterfeit or knockoff... Contact Apple Legal
https://www.apple.com/legal/contact/
Apple site warns against counterfeit third party (power) accessories (last year)
If the product were a Lightning cable or other item, there are several things
to check on the cable or case itself. There are support articles about these:
•Identify counterfeit or uncertified Lightning connector accessories - Apple Support
If the reseller wasn't an Apple store or authorized Apple reseller, it could be fake.
However there are uncertified channels where products get to market, which
may in fact be the officially sanctioned product. So this adds a wrinkle, too.
Good luck & happy trails! 🙂