sign

A sign is any kind of posted placard with information on it. Very often factual data can be found on billboards at construction sites or plaques on noteworthy buildings.

Almost any kind of data can be taken from a sign if it is judged to be reliable enough, although this judgment must vary according to the expected knowledge of the persons responsible for the sign.

The posted information is the evidence being cited. Its authority depends on the expected knowledge of the issuer about that fact; being displayed on a permanent plaque or a construction billboard does not by itself establish accuracy for every field.