English: Replication of English actor Matt Smith's authenticated signature as seen on signed autograph page of The Crown's Episode One script dated 9th December 9 2013
In the purview of the author, this signature is copyright-free in the UK and elsewhere therefore should be in public domain since a provision on Commons:PD-signature United Kingdom states that "...if the signature is extremely simple (eg a scribbled line or two), it will not be copyright even in the UK". The signature here is not complicated and consists only of very simple lines that can be replicated, thus it doesn't meet the threshold of originality
This signature is believed to be ineligible for copyright and therefore in the public domain because it falls below the required level of originality for copyright protection both in the United States and in the source country (if different). In this case, the source country (e.g. the country of nationality of the signatory) is believed to be United Kingdom.
Note that this tag cannot be used on all signatures, as not all signatures are copyright-free.