3 missals currently being printed that have pre-1955 (or 58) versions:
Fr. Lasance New Roman Missal (daily 1945, reprints with added feast days)
St. Andrew's Daily Missal (1945, 1949, 1953)
New Marian Missal (daily -- 1958)
The SSPX 1962 missal is made of high-quality paper and binding, and it has generally everything these other 3 have, but like explained above, it is different in several places, such as St. Joseph added to the Canon, the confiteor is missing before Communion, and Holy Week is slightly different, including the "perfidious Jєωs" prayer on Good Friday, which Pope John XXIII deleted.
I heard Fr. Gregory Hesse explain that the SSPX only went to the 1962 missal because of a controversy that erupted among several of the SSPX priests, who complained to the Pope over some kind of practice, and the Vatican used the opportunity to get the SSPX to agree to use the updated missal. Fr. Hesse believed that it was an unwarranted demand from Rome, because it had nothing to do with the controversy itself, but that Rome merely made a demand in a moment of weakness from the SSPX. I have noticed that Bp. Williamson and de Mallerais have used rubrics from the 1955 missal, even while their priests follow the 1962 missal. I don't know about Bp. de Galaretta or Fellay.
Fr. Hesse believed that Rome was simply using the 1962 missal demand as another means to cause division within the SSPX, because "divide and conquer" is a technique of aggression that works.
The changes that were going on in those days were leading up to the wholesale Novus Ordo of 1969, but rank-and-file Catholics would not have known what was in store down the road. Now that the principle of revision, change, and innovation has become established by practice and approval from Rome, there is literally no end in sight, as demonstrated by the recent approval of the bizarre and heretical NeoCatechumnal Way liturgical practices.