Some sad news coming from the world of Midtown relics. Prime Burger, the 74 year-old classic diner and burger joint across the street from St. Patrick's Cathedral, will soon close. An Eater tipster hears the last day is Saturday, but workers at the restaurant, which was a favorite of Sammy Davis Jr. and Rita Hayworth back in the day, say the final day is not yet decided, confirming that it will come sooner rather than later. The building, which the owners of Prime Burger own, is being sold. A worker today said fans of the restaurant should stop by to say their farewells, noting they should know more information about the closing date later this week.