For example, I have a document that has the signatures of three people, all public servants: a tax collector,an inspector, and a school principal. How could I collectively describe these three people?
This entry offers signatory but it implies a party to a contract.
Best Answer
(Props to @JLG for making me look this up.) Signatory need not refer simply to a party in a contract. While some dictionaries define it that way:
Others define it more broadly.
Notice, however, that these last three seem to be more layman's dictionaries than comprehensive ones. In light of this, it would seem that it is all right to use signatory in informal or non-official usage, but that a better word might be needed for official use.
Disclaimer: I am not a lawyer.