Ron: Master Mariner is just a model line for LeCoultre. I've never seen anything but dress watches marked Master Mariner. If the movement is truely a bumper automatic, that would probably place it in the 50's to early 60's. There used to be a LeCoultre brand for U.S. sales and Jaeger-LeCoultre for European sales. I believe that for a number of years, they have all been J.L. I've owned both and sometimes the J.L. will have a nicer finish than the domestic L. watch. They are a top-drawer company, making great watches themselves and for years made watches for Cartier under the name "European Watch and Clock Co.", made movements for Vacheron Constantin (you will also find LeCoultres assembled by V.C.), and made repeater movements for many big companies. I have two LeCoultres and love them. They are great investment watches.