
Parry densitometer
1970-1980
1970-1980
1978
1911
1993
circa 1930
1978
1978
1978
1978
1978
1978
1970s
1978
1978
1978
1978
1978
1950
1978
1924
1960
1900-1980
1960
1960-1965
1970-1975
1978
1978
1978
1978
1978
1978
1978
1978