C1 1948 Chain elevator digger vs spinner for harvesting potatoes
NAS 22 40 53 68 C1 1962 Periodic lifting top removal
NAS 22 40 53 68 C1 1963 Periodic lifting top removal
NAS 22 40 53 68 C1 1964 Periodic lifting top removal
NAS 22 40 53 68 C1 1965 Periodic lifting top removal
NAS 22 40 53 68 C1 1966 Periodic lifting top removal
NAS 22 40 53 68 C1 1967 Periodic lifting top removal
NAS 94 C1 1969 Rate of bulking