GPG is not compatible with PGP, unless of course you compile it yourself, and tweak the myriad of flags to make messages produced by it digestible to older PGP versions. And to make matters worse, it shoves all those somewhat novel and untested ideas up your throat whether you ask for it or not. On the other hand, GPG is a great hacking tool if you would like to explore the hidden mysteries of OPenPGP packets. Well, I've been happy with PGP 2.63i for years. File is encrypted.
Secret key is required to read it.