How do I identify/check my Apple charger serial number?

Apple does not provide a means for users to check the originality of their "Apple" power adapters via a serial number. These numbers could easily be faked.

If you purchased this adapter directly from Apple or an Apple Authorized Reseller, than it should be an original Apple device. If not, then it could be a fake.

Not a valid serial number.

Take the adapter in to the Apple Store and ask them to check the adapter.