They are a BS 2470:1973. The technical data for the material is that it is high tensile grade alloy steel, heat treated to RC39-43. The material has a
BSW (Whitworth) High Tensile Hexagon Head Bolts BS1083 Grade 'R' Zinc Plated
Everbilt 3/8 in.-16 x 2-1/2 in. Hex Socket Head Stainless Steel Socket Cap Screw 825458 - The Home Depot
British Standard Whitworth (BSW) nuts and bolts
5/16 3/8 1/2 BSW Whitworth capuchon haute traction tête boulons vis à douille EUR 5,47 - PicClick FR
3/8-16x1/2 Grade 5 Hex Head Cap Screw Zinc Plated
BSW 1/8 5/32 3/16 1/4 5/16Hex Socket Cap Screw High Tensile 12.9 Allen Bolt
5/16 BSW Whitworth Hex Set High Tensile R/ 8.8 Self-Colour DIN933 – Fixaball Ltd. Fixings and Fasteners UK
1/8- 5/32 - 3/16 - 1/4- 5/16 Bsw Brass Machine Screws - Round Head Slotted £4.99 - PicClick UK
1 PACK OF 10 - 3/4 Bsw (Whitworth) Nylon Insert Nuts £12.00 - PicClick UK
