This is a backstamp for Rosenthal Sanssouci porcelain china. 

• The mark includes the letters "R.C." with a crown above and crossed scepters below. 

• It was used by the German porcelain manufacturer Rosenthal on its popular Sanssouci line of dinnerware. 

• The Sanssouci pattern, known for its rococo style and raised scrollwork borders, was introduced in the early 1900s. 

• This specific mark dates the piece of china to the period between approximately 1896 and 1906