A half hour before departure at JFK, a mechanic showed up with a suitcase sized portable manual Loran C receiver and strapped it into the Captains flight bag space to his left and connected it by a 28VDC plug and an antenna connector. As co-pilot, I had to check it out which I did. The month I flew the trip I had a different captain each trip. None of them knew how to work the manual loran. Of course we had VOR-DME for about 350 nm of the 700 nm leg. The Captains would fiddle with it half an hour and give up. I could usually cajole them into letting me sit in the seat and "practice" getting a fix. You couldn't really miss Bermuda and there was no other airway traffic so if you got off course 50 miles it didn't matter. In practice we were never off more than about 5. This was when Eastern had applied to the CAB to fly to the Pacific.