Companion status can be established through several kinds of evidence: tawātur, widespread transmission, well-founded historical reputation, a reliable Companion’s report, a trustworthy Successor’s testimony, or, under conditions, a claim made by the person concerned.
Mass or widespread transmission: a historically well-established attribution supported by extensive reports.
Testimony from earlier transmitters: a reliable Companion or Successor identifies a qualifying encounter.
An individual’s own assertion: it can be investigated only where a meeting was chronologically possible and the assertion is credible.
A devotional honorific attached to a name is not, by itself, a substitute for determining the historical evidence behind that person’s classification.