1923, black overprints ''Ca.'' on Colombia SCADTA issue of 1923, complete set of 12, including overprint on registration stamp, nice and choice set, full OG, NH (15c, 30c, 50c,3p and R/20c) or previously hinged, mainly VF and very rare in complete set, C.v. $6,850, Unitrade C.v. CAD$8,850, Est. $3,000-$3,500 (Image)