I found this photo in a series of old negatives that I have. With my brother working  as an Engineer with Dredging Division, there were certain times I was able to get on site for good photo opportunities.  I took a whole series this day which captured a unique moment in time at the Balboa Dry Dock.  This was the last year of the Canal Zone, 1979.  PCC's rule was to dry dock floating equipment every four years for maintenance.  Here are both the Floating Crane U.S. Hercules in for maintenance and the newly purchased Railto M. Christensen dipper dredge in dry dock for hull repairs.  This dry dock crane was designed and constructed in 1907 by the American Hoist and Derrick Co., St. Paul, Minnesota.  I wonder if it still in operation today?  My brother told me that it was still working in '99, but with a air hose hooked to it.  The old steam boilers within must have gone to pasture.