(Route 5032) Louisville & Cincinnati, Mail Line. Feb. "21", red rectangular steamboat route agent datestamp with manuscript date on folded Merchants Bank of Cincinnati lettersheet datelined "20th February 1851" and addressed to Indianapolis Ind., bearing 5¢ red brown (1) cancelled by matching manuscript "X", four margins, tiny tear at top and barely affected by vertical fold, endorsed "Paid" and "Via Madison"; stamp lifted and replaced, a Very Fine usage, ex-S.W. Richey; with 1968 P.F. certificate, signed and guaranteed by Stanley B. Ashbrook. Towle No. O-21-g  Estimate $5,000 - 7,500. THIS IS THE ONLY RECORDED EXAMPLE OF THIS STEAMBOAT ROUTE AGENT POSTMARK USED WITH THE 5¢1847 ISSUE. In July 1846, the U.S. Mail Line of Cincinnati was contracted at $3,850 a year for a daily service between Louisville and Cincinnati. The contract was renewed every four years until 1858. The U.S. Mail Line was using the General Pike and one other steamboat for this service. This rectangular route agent marking with manuscript day of month was used in 1851 only. There are a total of three recorded 1847 issue covers with this rare boxed route agent marking:1. Feb. 21, 1851, 5¢ 1847 on letter from Cincinnati to Indianapolis Ind., ex-Richey, the cover offered here.2. Apr. 5, 1851, 10¢ 1847 cancelled by manuscript with red postmark on partial letter.3. Apr. 22, 1851, 10¢ 1847 tied by blue postmark and grid on cover to Philadelphia Pa., PFC. $0 (Image)