Many of these older Macallans are "Macallan-Glenlivet" bottlings from the 1930's, 1940's and 1950's (white label, red lettering at the top saying "Macallan Glenlivet") which have various ages.
I know of 1942 - 35y/o
1946 - 33y/o
1949 - 25y/o
1937 - no age statement
1957 'over 15 years old'
As for the OB editions:
Up to the 1959 edition, they were all 15 years old.
1960 to 1966 editions were 17 years old
1967 onwards have been 18 years old
In 2004 the bottle style was changed from what is referred to as "Classic" to the one now in use.
The last "Classic" label was produced in 2004 as a 1986 18y/o, but the same year also saw a limited production of 1986 18y/o new style.
I hope this helps,