I will sign your PGP/GPG master key if and only if:
I have seen 10 or more people accept your name as identifying you, and I can find 10 or more documents linking your name to your email address spanning one year or more and You show me your valid government-issued picture ID, while validating the hash, key id, and key length and Your master key and signed crypt key are published globally and You reply to my challenge email, quoting the challenge and signing the reply with the key you asked me to sign/certify.