No date on this photo but must be in the 20's.  Note the hill across the Canal is barren still from the construction days.  There is also a old dredge moored on the west bank.  Note also the power line towers on the Gamboa bridge.  There is a road section built on the bridge, but no road into the Gamboa area yet.  The vessel transiting the Canal is a old Naval vessel.  This photo is in bad shape, but is really good subject matter.