Medal commemorating first free balloon stratospheric flight of Professor Auguste Piccard and Dr. Paul Kipfer
1931
1931
circa 1920
1926
1921
1926
1930
1927
circa 1930
1931
circa 1920
1920
1920-1929
1934
1931
1932
1955; 1830
1921-1930
1934
1920-1925
1932
1933
1921
1925-1928
1920-1925
1927-1929
circa 1927
circa 1930
circa 1930
1925
1921-1926
1934
1924-1927
1922-1923
1922-1923
1922-1923
1922-1923
1920-1929
1927
1932
1920-1928
1920-1928
1923
before 1928
2000-100 BCE
1930-1931
Before 1932
1920-1930
1920-1930
1928
1934