This is annealed glass that is heat treated by raising its temperature to 700 degrees C and then cooling it more slowly than toughened glass.
It is not a Safety glass and breaks in a similar way to ordinary annealed glass. The process adds strength (twice that of annealed glass) and thermal safety.
It is of particular benefit when used to ensure the thermal safety of vertically glazed solar control glasses and cladding panels. There is very little risk of breakage due to nickel sulphide inclusions and if broken it will tend to stay in place and reduce the risk of falling glass.