I am new here, so forgive my lack of etiquette, but I need some knowledgeable advice on identifying a Mold Pattern for what I believe to be an authentically marked piece. It is floral, and very 3 dimensional, but doesn't appear to be any of the known or common patterns.

Welcome, There is no way I can tell you your mold pattern or #. If you have the real deal here many of these pieces did not have a pattern name. In all my RS prussia price guide books they are only discribed by dogwood flowers or whatever flower it is, or discribing the object on the item. None have an pattern name. Now one way to tell Rs prussia is it's weight. I don't know what your item is but lets say its a bowl, it should be light and very thin, very delicate. There is a lot and I mean A Lot of repo's. So compare the marks to real RS Prussia marks(Google Images) RS Prussia marks. Then look at website Porcelian & Pottery and more and click on fake marks, There is also other good sites but remember not all are correct.