according to ISO 898, part 1
1) The dot in the marking symbol may be omitted.
Identification with the manufacturer’s mark and the property class is mandatory for hexagon screws 4.6 to 12.9 and hexagon or hexalobular socket head cap screws 8.8 to 12.9 with thread diameter d ≥ 5 mm, where the shape of the screw always allows it. (Marking of bolts and screws are preferably on the head).
