Text on Flickr:
Photo showing foundations work for the old Bank of China building in early 50s. (My comment: the date is end of 1949/beginning of 1950 - see moddsey's comment)
Construction of the basement was in progress with a Scotch derrick as the only means of rigging heavy steel sections, which was required for the ELS work when excavation is getting deeper.
Scotch derricks were common in the old days when tower cranes were not popular, this type of crane can be found in local dockyards, casting yards and container handling yards as late as in mid-80s.
Jointing of the last bridge segement at mid-span of Ting Kau Bridge did make use of Scotch derricks, imported from Britain as second-hand equipment. 4 numbers were operated simutaneously to get the job done, which is probably the last time Scotch derricks used in Hong Kong.
Elsewhere in Bangkok, Taipei and Tokyo, Scotch derricks with modern safety devices and control consoles can still be seen, thanks to the popularity of building highrise structural framing that made use of steel sections.
The major shortcoming is that Scotch derricks can only slew 270 degrees maximum, it is forbidden to install a derrick boom within the quardrant between two raking struts.