Thank you for the additional information. I am accumulating very useful information for an eventual buyer. This is an interesting detective exercise.
I appreciate all the effort that has gone into providing this background. Based on your hard work I will ignore the serial # list and trust the much more persuasive proof markings and inspectors marks and date the gun to the 1940's.
That eliminates the easy "Medium Grade Gun" assessment based on the serial #. Is it necessary to identify a model number, or should I simply leave it up to the 'eye of the beholder' to determine it's 'grade'? That leaves the problem of finding 'comps' for pricing, but one step at a time.