Wie wäre es in einem Terminal (Eingabeaufforderung):
gpg --fingerprint <user_id>
Und von der gpg-Handbuchseite:
--fingerprint List all keys (or the specified ones) along with their finger‐ prints. This is the same output as --list-keys but with the additional output of a line with the fingerprint. May also be combined with --list-sigs or --check-sigs. If this command is given twice, the fingerprints of all secondary keys are listed too.