Mass. Gen. Laws ch. 53, § 97

All nomination papers shall be sealed up and filed with the secretary of the city or town committee not less than ten week days previous to the day on which the caucus is to be held for which the nominations are made, and he shall endorse upon them the time when he received them. They shall not be opened until the time for their filing has expired, when the secretary, at his office, shall publicly open them and publicly announce the nominations therein made.