Questions 

Was this on the North or South breakwaters?

Does any trace remain today?

Presumably the crane was built as a block-setting crane for construction and repair of the breakwater itself. It is common for such cranes to be left in place afterwards.  Was it ever used as a port crane, for freight handling? This would be unusual - such large cranes, especially when steam powered, where too inconvenient to last much past WWII and were nearly always ignored or replaced by electric cranes or road mobile cranes.