Please re-shoot maker mark in rectangle and embed image. 1927 was the year of the study of plate marks, in use long before that...see Ref. article on number marks for plated wares: https://www.925-1000.com/a_platenumbers.html
French platers marks (oriented in rectangle/square shape, not diamond) might include "O" for Orfeveries or Orfevres before name intial (like your R). But we cannot be sure here without a better image. There are also many pages in this site of French Advertisements with some firm names listed within.