Medal commemorating first free balloon stratospheric flight of Professor Auguste Piccard and Dr. Paul Kipfer
1931
1931
1935
1930-1940
1930
1940
1938
1940
1938
1938
1938
1935
1938
circa 1930
1940
1931
1935
1940
1936
1934
1936
1931
1937
1937
1935
1938
1938
1932
1955; 1830
1934
1930-1940
circa 1938
1935
1932
1933
circa 1930
circa 1930
1930-1940
1936
1934
1935
1932
1938-1940
2000-100 BCE
1930-1931
Before 1932
1937-1938
1937-1937
1937-1938
1934
1938 and 1951