On the US east coast, harbor defenses were guarded by so-called "Gate Examination Vessels." These were small, armed ships, sometimes converted lightships such as the Nantucket (LV-112). They were armed with a 3" deck gun and several 0.50 cal. heavy machine guns, painted grey, had their hull portholes blanked off and light and RDF beacons removed. The Nantucket was taken off her station from Nantucket Shoals and served as the Portland, Maine Gate Examination Vessel in the later part of WW II.