Ball stamp
/ˌbɔːl ˈstamp/(also Ball's stamp) Now historical
noun
A stamp mill utilizing a steam hammer, formerly used in the United States for crushing ore.
Origin
Mid 19th century; earliest use found in Mining Magazine & Journal Geology. In some forms from the genitive of the name of W. Ball, the inventor + stamp. In some forms from the name of W. Ball + stamp.