Pillbox 126, Tung Yeung Shan [1937- ]
Very rough guess at the location, based on these notes from Rob:
That  picture would appear to be PB 126, the give-away being the three air-shafts protruding from the roof. All of the known PB's on the mainland were either one or two loophole type (126 and 315 being the exceptions) with appropriate airshafts. 126 still exists in ruined form adjacent the road that comes off Fei Ngo Shan Rd and goes down past Gilwell Scout Camp. Construction of the road savaged 126, and it is also heavily overgrown (Apr 2011). There are at least 10 PB's within one Km of that spot.
Additional notes from Rob:
Year completed is: Approximate
Condition at last visit: Ruin
Date of last visit: Feb-1995