But Mad North-Northwest
Well I learned something today:I believe the original photo identifies this as a DIN 6921 class 90 fastener.
Fastenal and others carry these.
"These self-locking hexagon flange bolts are designated property class '90' or '100'. The flange bolts are case hardened in order to perform their self-locking function, and therefore cannot be classified as property class 9.8 or 10.9, although their tensile strength is at least 900 resp.1040 MPa."
Looks like the torque spec for an M8 class 90 bolt is 34Nm, or 25 ft-lb.