Years 1965-1972 = the first 1 or 2 numbers = the month (1-12)...the next number = the last number of the year...the rest of the numbers are the instruments number ...
Year Approx. Number
1949-1950 =3000
1951 =4000-5000
1952 =5000-8000
1953 =9000-12,000
1954 =12,000-16,000
1955 =17,000-21,000
1957 =22,000-26,000
1958 =27,000-30,000
1959 =30,000-34,000
1960 =34,000-39,000
1961 =39,000-45,000
1962 =46,000-52,000
1963 =53,000-63,000
1964 =63,000-77,000
1964-early 1965 =77,000-84,000
