Confederacy, Danville Prison, Building #4, Danville, Va. Small 1864 folded letter to Waterboro P.O. in Ohio, across the lines with "Old Point Confort, Va., Apr 19" cds and matching straight line "Due 3" handstamp, endorsed "Prisoner Letter" at right, letter datelined "Danville, Va., March the 21, 1864" with sending address "Danville, Va., Prison No.4, Via Fortress Monroe", Very Fine, am extremely rare usage from Danville Prison #4, only five such covers from this prison known, pictured in Harrison (Prisoners' Mail From The American Civil War, page 74). Estimate  $1,500 - 2,000. $0 (Image)