(Early Mississippi & Teche River Mails) Steamboat Rates, two covers, first folded letter datelined "Point Coupee 21 January 1824" to New Orleans La. where manuscript "SB 18½" rating applied for 165 miles on the Mississippi as a post road, some taped separations and ink erosion; second folded wrapper dated "1827" and endorsed "with Bill of Lading" from New Orleans La. to Opelousas La. via the Mississippi, La Forche and Teche Rivers, manuscript "S/B 37½" double weight rating, Very Fine. Estimate  $300 - 400. It became standard practice for postmasters to indicate the arrival of a letter by steamboat to use the abbreviation "SB" prefixing the payment due. $0 (Image)