Someone asked me recently if I knew where the origins of the Bracha of Shalom Rav (instead of Sim Shalom at Mincha and Ma'ariv) are from. As far as I knew the Nusach is not found in the Gemara nor the Rambam. The only real lead I could find was from the book Jewish Liturgy and its Developments by Abraham Zebi Idelsohn (taken from Google Books):
Shalom rav is another version of the prayer for peace. It is now used in the Ashkenazic ritual for the Minha and Maariv services. It is first mentioned in the eleventh century, and was first introduced by M. Rothenberg. However, as Dr. Finkelstein rightly points out, the fact that Provence, Avignon, and Carpentras have only this version for all services would indicate that it is very old.
The footnote is not available in the excerpt. I was wondering if anyone had any more information on the origins of this Nusach, or how to find more information from the excerpt I found (eg. is there a Siddur of Meir of Rothenburg that I don't know of; who is Dr. Finkelstein?).