HCOTEG121270 - Marking: Law: Hydrocarbon Oil Regulations 1973
Overall, these regulations deal with premises and plant for the production of oil - in general this means refineries.
They also cover measurement - note that section 51 was added by the Hydrocarbon Oil (Amendment) Regulations 1993 SI 1993/2267
For further details of the Hydrocarbon Oil Regulations (HOR) see HCOTEG31750