I want to know the answer to the following question:
What were revised between 1951 and 1955?
All the background I'm provided with is that "After the Vatican Council, in April 1969, Paul VI approved the "new Order of Mass" promulgated in 1970, as stated in the Acta Apostolica Sedis to "end experimentation" with the Mass and which included the introduction of three new Eucharistic Prayers to what was up to then a single Roman Canon.". Is that enough to answer the question?
Answer: no