A used block of four United States 1-cent Fort Dearborn stamps from the 1933 Chicago Century of Progress Exposition Issue, Scott #728, printed in yellow-green with a view of the restored Fort Dearborn blockhouse, inscribed 'CHICAGO CENTURY OF PROGRESS / 1833–1933,' flat plate, perforated 10½ x 11. The top two stamps carry a bold double-ring circular datestamp cancel; the bottom two bear heavy bold wavy machine/killer bar cancels that significantly obscure the designs. Exterior perforations and gutter perforations appear intact on all sides; color is fresh and vivid; the reverse shows clean cream paper with no visible hinge remnants, though minor wrinkling is present. Please review the scans for condition.