The permission for "priests over 70" was given in 1970, I think, but the Masses had to be "private" and Paul VI emphasized that the bishops had to be very sparing with the permission. Mgr. Alfred Gilbey was saying it in London, as he was over 70, but he wasn't supposed to have people present. But it was a new and impossible distinction.
There were at least three retired priests saying Mass in Germany, one in the chapel of the Franciscan nuns of Perpetual Adoration in Mainz, another in a private chapel in Mainz and another in a side chapel of Munich cathedral. And Fr. Hans Milch, aged 47, in his parish church at Hattersheim outside Frankfurt. The bishops were turning a blind eye, but all were ordered to stop in 1976. Fr. Milch was the only one to continue. (I will post some of his writings soon.)
In America Fr. Gomar de Pauw? Did he have permission?
In England Fr. Oswald Baker was continuing in his parish church in Downham Market in Norfolk.
And all the priests in the Diocese of Southwark near London, possibly. The English Bishops had decided on the First Sunday in Lent 1970 for the introduction of the New Mass. (The Bishops' Conferences in each country could set a date between 30 November 1969 and 28 November 1971, thanks to the Ottaviani Intervention. Before that, it was to have been Nov. 1969.) One English Bishop, Cyril Cowderoy, Archbishop of Southwark, delayed it on his own initiative until 29 November 1970.
And an Archbishop in Fribourg in Switzerland also delayed it on his own initiative, but with the tacit approval of the local bishop.