Both inserts below were taken from 1963 lighters. Close examination reveals some minor differences to the typeface used, On the lower image, in both occurrences of the word "ZIPPO" the word has expanded in length, but shrunk in height, also notice the difference in the "O". In the lower image, a perfect circle, whereas in the upper image it is elliptical. The size of both the Pat. number and the Registered Trademark symbol (®) have also changed.
There are 4 possible combinations as indicated in the table below. I have seen various combinations in all years between 1961 and 1975 and all combinations have been noted with both the hollow and solid rivet.