Re. KMJL12s post: Certainly, that is a great list, endorsed by the current rubrics and regulations. My list was not meant to be exhaustive, by any means; there are indeed a host of items.
I am not certain I agree with Sts Alive that the OF has limitations in being a “measuring stick;” rather I feel that *Sacrosanctum Concilium *itself must have that role—as any form of the sacred Liturgy cannot sufficiently define itself in objective reference to its development.
I would submit that the provisions in SC, which the overwhelming majority of the Council Fathers voted for, could not easily be “retro-fit” to the pre-Conciliar Order of Mass. (In a sense, it would be like trying to outfit a Navy frigate from the 1900s with twenty-first century radar, launch systems, fire-control, environmental support, etc. Given the technology, a shipbuilder would find it easier to take a basic modern ship design and build the new parts into it.)
Except for the prayers at the foot of the altar (at the start of Mass), and the readings said from the ambo (rather than from the body of the sanctuary), and the elimination of the Last Gospel—the first and last practices being originally part of the priest’s private preparation—as far as the perspective of the congregation, I would suggest that there is relatively little difference. As far as the text of the Ordinary, even in Latin, 90% of the Order of Mass Pope Innocent III (c. 1200), which forms the basis of the pre-Conciliar rites of the last millennium, is intact in the Missal of 1969. Even all the old prefaces have been retained, along with new ones that were added. The greatest difference, which would be missed by the congregation when taken “in secret,” are the presentation prayers for the bread and wine. (Admittedly, there are some differences in the propers, most are identical to the OF, some have been placed differently, and a number have been edited—some good, some WAY not so good.)