1. Bench-marks. Descriptions and elevations of precise level, Panama Railroad, and other bench-marks between Colon and Panama City, Isthmus of Panama; corrected and revised to Apr. 1, 1928. Bookmark Corporate/Agency Authors: Operation and Maintenance Department and Panama Canal Publisher: Operation and Maintenance Department Date: June 27, 1928 SuDoc number: W 79.2:P 91