Medal commemorating first free balloon stratospheric flight of Professor Auguste Piccard and Dr. Paul Kipfer
1931
1931
1935
1930
1938
1938
1938
1938
1935
1938
circa 1930
1931
1935
1936
1934
1929-1935
1936
1931
1937
1937
1935
1938
1938
1932
1955; 1830
1934
circa 1938
1935
1932
1933
circa 1930
circa 1930
1936
1934
1935
1932
2000-100 BCE
1930-1931
Before 1932
1937-1938
1937-1937
1937-1938
1934
1938 and 1951
1929-1935
1935
1933
1936
1939
1935
1934