2 Answers

Main Entry: token  [toh-kuhn] 
Part of Speech: noun
Definition: indication, remembrance
Synonyms: badge, clue, demonstration, earnest, evidence, expression, favor, gift, index, indicia, keepsake, manifestation, mark, memento, memorial, note, omen, pawn, pledge, presage, proof, relic, reminder, representation, sample, security, sign, significant, souvenir, symbol, symptom, trophy, warning, warrant

A "token" is also a coin used for admission, so "ticket" or "admission" might be acceptable. It depends on how you are using the word in your sentence. 
I needed a "token" to board the subway.  I needed "admission" or a "ticket" to board the subway.  

I got a pressed penny from the Empire State Building as a "token".  I got a pressed penny from the Empire State Building as a "souvenir".