I don't think it is his certificate, I think it is the grandson's certificate as it is definitely in BMD as George Anthony, March quarter 1848 Upton upon Severn 18 [53]41. So unless the mistake occurred twice - in the registration and on the certificate it seems there were two George Anthonys.
When did it become a legal matter to register children? As Jim1212 said the elder children don't seem to have been registered either.
Jan