The final post on this honest. Having promised to let the Argyle Archive have any of my programmes they want I found the Official Handbook for 1962-63. Like Wisdens they list all matches and I can definitively state that the quoted attandance for the reserve match against Tottenham was, as said earlier, 12,907 on 20th January 1962 the attendance for the Mansfield reserve match was 25,648. Looking through normal attendances for reserve matches was in the 2,000s.
As an aside when Jimmy Greaves was down at Home Park for the first time our senior team were playing at Anfield and losing 2-1 with A'Court and St John scoring quite a coincidence that Saint & Greavesie played and scored against Argyle on the same day.
When we played Liverpool at Home Park on the final day of the season Argyle lost 3-2 with A'Court and St John scoring with a certain Roger Hunt getting the third. I remember this match as having a wonder goal from George Robertson. Only 13,427 though in attendance.