@wineview I believe your number interpretation is correct for the Owens Illinois carboys.
For the 7gal carboy the VR indicates the manufacturer Vidriera los Reyes of Mexico. The M3008 is the DOT manufacturer registration number
The DOT-1M number indicates the carboy construction specification 1M; non-reusable glass carboy in non reusable expanded polystyrene packaging, and meets various requirements including the carboy may not exceed 6.5 United States gallons nominal capacity, 7.0 ,United States gallons overflow, tolerance plus or minus 10 fluid ounces.
According to the regulation, some additional requirements for DOT-1M are listed below.
(1) Each carboy must be machine blown with threads in the neck of the glass carboy for closing by a screw cap.
(2) Each carboy must be annealed and have a real temper not greater than 5 based on ASTM C148-77, test Method A, using polariscopic examination.
(3) The weight of each carboy must be 14 pounds or greater with a tolerance of minus eight ounces.
(4) Meets the 4 foot drop test requirements when full and packaged etc.
(5) Meets the hydrostatic test requirements, 40 p.s.i.g. instantaneous or 13 p.s.i.g. for one minute.