Articles by Ryan are here.
When it comes to deciding whether strengths are signature strengths, if you have only one question to ask someone, make it:
“What strengths are most essential to who you are and define you as a person?
This appears to be the single most important criterion in determining whether character strengths are “signature,” or not. Other questions such as, “Is the strength energizing?” “Is it easy to use? and “Is it used across settings?” are important, but are subsumed under this more important question. If you want to get to the heart of the matter, ask about identity.