How to check if an adapter is original

There is no serial number check to prove they are real. The counterfeiters simply copy all markings/serial numbers of legitimate accessories and is the easiest part of producing a fake product. With the counterfeit market of Apple accessories being huge, the only way to know you have a legitimate accessory is to purchase from Apple or Authorized Apple Seller.

To "solve my problem" only purchase power adapters either directly from Apple or an Apple Authorized Reseller.

Counterfeit adaptors — while often outwardly indistinguishable from genuine products — can cause performance issues and even be outright dangerous.

Don’t skimp.

Buy a genuine product from an Apple-authorized source.