Read this: Unaspirated or tenuis consonants are occasionally marked with the modifier letter for unaspiration ⟨◌˭⟩, a superscript equal sign: ⟨t˭⟩. Usually, however, unaspirated consonants are left unmarked: ⟨t⟩.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): How are unaspirated or tenuis consonants sometimes marked for unaspiration?
with the modifier letter