BSW Thread Hex. Head Bolts G4.8 Z/PL

European union established to metric threads as standard, to all constructions, instead of imperial (inch) threads.
BSW is an imperial-unit-based screw thread standard, devised and specified by joseph whitworth in 1841 and later adopted as a british standard. It was the world’s first national screw thread standard.
The threads BSW, UNC, UNF, BSF now are used only for restoration of old damaged goods in order to be authentical as the original at that time.