(Route 5032) Louisville & Cincinnati, Mail Line. June "5", blue rectangular steamboat route agent datestamp with manuscript date and matching "10" rating handstamp on circa 1851 orange buff cover addressed to Philadelphia Pa.; light vertical creases, Very Fine. Towle No. O-21-g  Estimate $1,500 - 2,000. A RARE EXAMPLE OF THIS STEAMBOAT ROUTE AGENT MARKING IN BLUE THAT WAS USED IN 1851 ONLY. $0 (Image)