All of Marshfield’s liquor stores passed a recent sting operation by police. On the last Friday in June, the Police Department sent two sting teams into the community, each accompanied by a person under 21 who attempted to buy alcohol at package stores, according to police Lieutenant Michael McDonough. “We try to make it fair,” he said. “We don’t want a kid who’s 20 years old who looks like he’s 35.” Normally, police test liquor stores and restaurants at the same time, and at least one establishment fails. But this time, when the town’s approximately 15 liquor stores were tested, all of them passed. McDonough said this is the first 100 percent passage rate he has seen in seven years of doing this kind of work. Stores that fail can face sanctions from the Board of Selectmen, including suspension of their liquor licenses.