English equivalent of "令牌"?
This '令牌敲响‘ is confusing. Possibly, the author was thinking of, or referring to a metal plate similar to a cymbal, maybe hanging on a string, which could be hit with a stick to produce a sound. The old guy hit it to drive out the demons. Sure would drive me crazy! 'Out out damn spot!'

I would translate '令牌‘ as 'badge of authority', or maybe here 'cymbal of authority'.