Medal commemorating first free balloon stratospheric flight of Professor Auguste Piccard and Dr. Paul Kipfer
1931
1931
1935
1926
1926
1930
1927
1935
circa 1930
1931
1935
1936
1934
1929-1935
1936
1931
1935
1932
1955; 1830
1934
1935
1932
1933
1925-1928
1927-1929
circa 1927
circa 1930
circa 1930
1936
1925
1934
1924-1927
1935
1927
1925-1935
1932
1925-1935
1923
before 1928
2000-100 BCE
1930-1931
Before 1932
1928
1934
1925-1935
1927
1929-1935
1935
1933
1936
1923