Can I tell if someone has the talent?

[Leon tilts his head at the question, frowning faintly before reaching up to scratch his chin. His eyes are fixed on Isamu, curious.]

Not just by looking at a person, no. Usually a person first manifests their power in a display of significant symbological force in some way -- accidentally or intentionally, like through a test. Some people get the tattoos before they actually know if they have any decent talent for Symbology.