This is a photo of the lower Miraflores Locks construction.  The photo is from around January 1912 time frame.  I have determined this through other photo sources. There were two chamber cranes at both Pedro Miguel and Miraflores.  They were used not only for placing cement, but also for moving the steel and wooden forms necessary in construction.  Each crane weighed  95 tons, was mounted on four freight cars and moved on tracks along the bottom of the lock.  The operator was housed in a cage atop the crane.   Gatun Locks used a cable and pulley system instead of the chamber cranes.