Greetings,
I inherited a 1958 GMT master ref. 6542 from my Grandfather who passed away in 2013. He purchased the watch new in 1959 In Rammstein Germany while in the Air Force. He was a career pilot and I imagine he picked this watch out because it was a useful tool for a pilot to have.
In the 70’s the original bezel broke and his watch service ship installed another submariner style bezel on it( I imagine back then without the internet it was harder to source parts). He also replaced the original bracelet( may have broke or who knows). He put a JB Champion brick bracelet on it as you seen in the photos.
I purchased a Bakelite replica bezel for it, And plan on getting a genuine 7206 with 58 end links (if I can find the right deal). He wore the watch for over 50 years and it has held up wonderfully. The dial and hands are original.
Here are some photos of the watch, along with a picture of my Grandfather wearing it in 1965 or 66. He worked for the test flight program at Edwards Air Force base in the 60s and 70s after he retired and wore the watch daily. So the watch has some very cool Flight related history as well.