Note: every manifestation of a letter is counted, so the number of documents in a repository may be larger than the number of letters.

Repository Number of documents Further details
Ratsschulbibliothek Zwickau 2 City: Zwickau
Country: Germany
Real Academia de la Historia - Alternative names for repository: RAH
City: Madrid
Country: Spain
Regionaal Archief Alkmaar 1 City: Alkmaar
Country: Netherlands
Regionaal Archief Dordrecht 3 Alternative names for repository: Regionaal Archief Dordrecht (with Huis Van Gijn, Het Hof, and Dordrechts Museum) Municipal Archives, Dordrecht
City: Dordrecht
Country: Netherlands
Remonstrantsche Kerk 1 Alternative names for repository: Remonstrant Church Amsterdam Remonstrantsche Kerk
City: Amsterdam
Country: Netherlands
Rigsarkivet 4 Alternative names for repository: Danish National Archives
City: Copenhagen
Alternative names for city: KĂžbenhavn
Country: Denmark
Riksarkivet 15 Alternative names for repository: Riksarchivet
City: Stockholm
Country: Sweden
Rosenbach Museum and Library 5 City: Philadelphia, PA
Country: United States of America
Royal Astronomical Society 6 Alternative names for repository: RAS The Royal Astronomical Society
City: London
Country: England
Royal College of Physicians of Ireland 37 Alternative names for repository: RCPI
City: Dublin
Country: Republic of Ireland
Royal Greenwich Observatory Library 6 City: London
Country: England, United Kingdom
Royal Institution of Cornwall - City: Truro
Country: England, United Kingdom
Royal Irish Academy 21 City: Dublin
Country: Republic of Ireland
Royal Society Library 3036 Alternative names for repository: RS The Royal Society
City: London
Country: England, United Kingdom
Russian State Archive of Ancient Acts [RGADA] - City: Moscow
Country: Russia