Additional self-signature

[Oskar L.]

Werner wrote:
> When importing a secret key into a keyring without a public key, a
> public key is created from the secret key.  Due to historic reasons
> the self-signature on the secret key is a different one than the one
> created with the public key.  How when importing the public key a new
> signature will be added and gpg is not able to detects this.  This
> won't harm because the signatures are effectively identically although
> not bit wise.

So why do I also get a second self-signature when I first import the
public key and then the secret key? Surely some kind of secret key can't
be created from the public key? Also, when I delete secring.gpg, why is it
recreated when I import a pubic key?

Oskar