United States and Brazil Mail Steamship Company
The United States and Brazil Mail Steamship Company operated between New York, St. Thomas, Pernambuco, Bahia, and Rio de Janeiro, from 1865 until 1875.
Saint Lucia, August 7, 1868, endorsed "pr United States Mail Steamer" sent under cover per RMSP Mersey, departing Saint Lucia August 9, arriving St. Thomas, August 12, 1868. At St. Thomas a forwarding agent applied the 10¢ green 1868 E Grill prepaying the 10¢ steamship rate per United States and Brazil Mail Steamship Company Mississippi, departing St. Thomas August 14, and arriving New York August 20. Postmarked on arrival, New York, New York, August 21, 1868. 
Pernambuco, Brazil, October 1, 1870, franked with 200r stamp, per United States and Brazil Mail Steamship Company South America, arrives New York, October 20, 1870, N.Y. Steamship 10 October 21 marking.
Puerto Rico, May 13, 1872, Porto Rico May 13, 72 PAID british PO marking, franked with 4 pence vermilion plate 12, canceled by “C61", St. Thomas May 14, 1872 transit, per United States & Brazil Mail Steamship Co. North America depart St. Thomas May 14, arrive New York May 20, N.Y. Steamship 10 due marking, Sismondo Cert.
Royal Mail Steam Packet Co. Connecting With
United States and Brazil Mail Steamship Co.
Buenos Ayres, Argentina, September 14, 1873, per Royal Mail Steam Packet Neva, manuscript 4d British debit to the United States, departed Buenos Ayres September 14 and arrived Rio de Janeiro September 23, transferred to United States and Brazil Mail Steamship Co. South America which departed Rio de Janeiro September 25 and arrived New York October 21 (NY datestamp error “Aug” instead of “Oct”) due 18¢ converted to 19¢ depreciated currency.
French Ligne K Connecting With
United States and Brazil Mail Steamship Co.
Montevideo, Uruguay, November 14, 1866, Edmd Barthold & Co Montevideo stamp, endorsed per steamer francais, most likely French Ligne K, Carmel, departing Montevideo November 15, 1866, E.J. Albert & Co. Rio de Janerio forwarding stamp, enters the mails Rio de Janeiro 24 November, 1866, (possibly a French Ligne K marking), placed on United States and Brazil Mail Steamship Co North American, departed Rio de Janeiro November 25, 1866, arrived New York December 22, 1866 New York "STEAMSHIP 20" marking, double 10¢ incoming steamship rate, regardless of distance.
Buenos Ayres, Argentina, November 12, 1868, Buenos Ayres Paq. Fr. K French Mail marking, per Ligne K Paquebot Aunis, departed Buenos Ayres November 12, transferred in Rio de Janeiro to United States and Brazil Mail Steamship Co. Merrimack, which departed Rio de Janeiro November 25 and arrived New York December 23, double weight letter indicated by manuscript ”2" rated 25¢ due (18¢ per 1/4 oz, 25¢ per ½ oz.).