a) a very specific list of requirements, that just happens to match a specific person. Definitely not any choices of language in the list, but possibly degree or equivalent experience if necessary.
b) be posted in a newspaper and on their main jobs page, but not widely elsewhere
c) ask for submissions by mail only, by a certain date
B and C are more telling than A though, because a weird list of requirements could be just someone weird, but narrowly posting and requiring applications by mail are part of exactly following the rules for demonstrating lack of candidates.