Larkspur Colo May 11. Black cds on circa 1872 cover to Castle Rock, C.T. franked with 3Ā¢ Bank Note tied by target cancel, slightly reduced at left, F.-V.F., Larkspur was located on the Denver and Rio Grande Railroad, about halfway between Denver and Colorado Springs. EstimateĀ $75 - 100. $0 (Image)