Currently for my email address exist 2 PGP keys on the keyservers. I want to remove one of them.
How do I do this?

Do I really have to revoke the unwanted key?

Originally I don't want to revoke this second key (I just want to use this internally)
and want to show only one (the primary) key to the outside world

OK, assume I revoke a public key on a keyserver. Is this key then visually removed
or does it persist (but only with a "revoked" flag) ?