How to check if an adapter is original

The only useful way to know if a power adapter is genuine is to purchase the product from an authorized Apple dealer.

Otherwise, your only other option would be to saw open the adapter to inspect the internal components and compare them to the internal components of another adapter which you know is genuine.

Unfortunately, if you do this, you will lose the use of 2 adapters.

For future reference, if you took the time to do a search on this forum on this exact topic, you will find literally hundreds of posts with basically the same answer: The only way to know for sure that you have an original Apple device is to purchase it either directly from Apple or an Apple Authorized Reseller.