Information:  - The Philadelphia Experiment is an alleged military experiment supposed to have been carried out by the U.S. Navy at the Philadelphia Naval Shipyard in Philadelphia, Pennsylvania some time around October 28, 1943. The U.S. Navy destroyer escort was claimed to have been rendered invisible (or "cloaked") to enemy devices.  - Destroyer escort (DE) was the United States Navy mid-20th century classification for a warship designed with endurance to escort mid-ocean convoys of merchant marine ships. "Kaibkan" were designed for a similar role in the Imperial Japanese Navy. The Royal Navy and Commonwealth forces identified such warships as frigates, and that classification was widely accepted when the United States redesignated destroyer escorts as frigates (FF) in 1975. Destroyer escorts, frigates and "kaibkan" were mass-produced for World War II as a less expensive anti-submarine warfare alternative to fleet destroyers.  - HS Leon ( D - 54 ) ( Greek :  /   , `` Lion '' ) was a Cannon - class destroyer that served with the Greek Navy between 1951 -- 1992 . The ship had formerly served with the United States Navy under the name USS Eldridge ( DE- 173 ) , famous for its alleged role in the Philadelphia Experiment .  - Pennsylvania (Pennsylvania German: "Pennsylvaani"), officially the Commonwealth of Pennsylvania, is a state located in the northeastern and Mid-Atlantic regions of the United States. The Appalachian Mountains run through its middle. The commonwealth borders Delaware to the southeast, Maryland to the south, West Virginia to the southwest, Ohio to the west, Lake Erie and the Canadian province of Ontario to the northwest, New York to the north, and New Jersey to the east.  - Philadelphia is the largest city in the Commonwealth of Pennsylvania and the fifth-most populous city in the United States, with an estimated population of 1,567,442 and more than 6 million in the seventh-largest metropolitan statistical area, . Philadelphia is the economic and cultural anchor of the Delaware Valleya region located in the Northeastern United States at the confluence of the Delaware and Schuylkill rivers with 7.2 million people residing in the eighth-largest combined statistical area in the United States.  - The Navy Yard, formerly known as the Philadelphia Naval Shipyard and Philadelphia Naval Business Center, was an important naval shipyard of the United States for almost two centuries. It is now a large industrial park that includes a commercial shipyard, Aker Philadelphia Shipyard.    Given the information, choose the subject and object entities that have the relation of 'instance of'.
Answer:
greek destroyer leon  , destroyer escort