If you are not already a member I would encourage you to join the American Air Mail Society. There are a number of experts on Trans-Atlantic airmail there. Their website is https://www.americanairmailsociety.org/ The annual dues for international members is the same as for US members if you chose to receive the monthly journal by email - US$30.
Here is a cover that happens to have this stamp that I wrote about in a recent issue of the Air Post Journal. This was flown on the first Trans-Atlantic flight by Pan American Airways, which was the airmail service for which this stamp was created and issued. This particular example is quite rare as it is autographed by the captain (Arther E. La Porte) plus 11 of the 13 crew members.