The crowned "R" stands for Rio de Janeiro, although it is not any sort of official mark. The maker "FJC" is Francisco José da Cruz, working in Rio 1854-1859. (By the way, the fineness of most Brazilian silver of this period was 10 dinheiros: 10/12 or .833)
An example of the work and mark of Francisco Pereira da Fonseca of Rio de Janeiro:
F/PF - 10
Member blakstone wrote:
This is Brazilian, made by Francisco Pereira da Fonseca of Rio de Janeiro, working at least 1864 to 1887. The "10" is the fineness of 10 dinheiros, 10/12 or .833.
Ref: Rodrigo Melo Franco de Andrade ed. As Artes Plasticas No Brasil (Rio de Janeiro, 1952) p. 258