
Obsidian possibly used in trephination experiments
1918-1920
1918-1920
1917
1919
1923 - 2015
1920 - 2007
circa 1920
1920
1924
1918
1916
1917
1918
1924
1955; 1830
1918
1918
1916-1917
1922-1923
1922-1923
1922-1923
1922-1923
1921
1920
1924
1921
1923
1934
2000-100 BCE
circa 1920
1923
1922
1920
1917-1918
1920
1920
1920
1903 (original); 1982 (model)
1772 (original); 1919 (model)
1990-96
circa 1920
1830 (original); 1967 (model)
1952-3
circa 1920
1924
1917-1918
circa 1917
1922-1923
1922
1922-1924
circa 1919