Barrack related plaque? [????- ]

Passing by this plaque in 2014 when the inscriptions on it were still quite legible, however, I didn't have any pictures of the whole plaque, for my attention was only on the training ground behind the fence, not outside of it.

But now it seems that there's a layer of white paint on it in the Google Street Map, does anyone have a recent photo of it? What's the nature of this stone?

San Wai Barrack

https://maps.app.goo.gl/uUc92zwjWKTGiTi7A