The first test was to see why there is a different count of players between the 1971 file and another copy on Old in Chess (OiC). I determined that all of the players on OiC are on my new file (WCC), but the WCC file lists three additional players. There are many other differences, especially in the spelling of names. Two of over 160 examples are WCC: 'Tseshkovsky, Vitaly V', OiC: 'Cheshkovsky, Vitaly', and WCC: 'Vinje-Gulbrandsen, Arne', OiC: 'Gulbrandsen, Arne'.
There are also small differences in the number of titled players. WCC lists 83 GMs and 178 IMs; OiC lists 82 GMs and 172 IMs. The ratings for the 589 players found on both files match perfectly, and that is what really matters. It is clear the files have a common source, but have been massaged by different hands. The numbers of players on the four new files are as follows:
Except for 1974, when many women disappeared from the list, this compares favorably with growth for the rest of the first decade of FIDE ratings:
Some numbers for subsequent years are 1990: 7786, and 2000: 33383. This compares with 87562 names on the January 2008 FIDE rating list, including 1109 GMs and 2808 IMs.