I am trying to confirm exactly the model and year, and grade of my gun. It is a 12 guage with a serial number in 151000 to 155000 range. It is a hammergun with the "F" grade stamped below the serial number. Were the numbers such as No.00, 0, 1, etc. only assigned to hammerless style guns? What would be the actual "catalogue style" description of the gun-ie "Back Action", Model ____, 1907 12 gauge ? Any other information would be appreciated.