YOU SAID:

The custom is to place an old coin in a dead mouth

INTO JAPANESE

古い硬貨を死んだ口に入れるのが習慣です

BACK INTO ENGLISH

It is customary to put an old coin in the dead mouth

INTO JAPANESE

死んだ口に古いコインを入れるのが通例です

BACK INTO ENGLISH

It is customary to put an old coin in the dead mouth