This is a size of 50mm diameter of pin for the passenger of Lufthansa Airlines when Luthansa used DC-10 aircraft for service on route of Vancouver - Calgray - Frankfurt in 1970's and said "try me wide-body".

The McDonnell Douglas DC-10 is an American three-engine medium- to long-range wide-body airliner, with two engines mounted on underwing pylons and a third engine at the base of the vertical stabilizer.