Thanks, Gary, for riding to the rescue! And Thanks, Ralph, for the kind words.
The reality is that the defining feature of the Model of 1902 is the round butt, and the defining feature of the Model of 1905 is the square butt. The butt configuration is the defining, and only, difference between these two Models; they are otherwise identical guns.
The 5th frame screw came after the introduction of the Model of 1905. There are about 4000 .38's made during this 'gap', some 1902's and some 1905's, all with 4-screw frames. The 5th frame screw is an engineering change, not a model definition.
The nomenclature of Neal & Jinks delays the recognition of the Model of 1905 until the introduction of the 5th frame screw, and at that point, drops the Model of 1902. From this point on, everything is a Model of 1905 - regardless of butt configuration. This practice is inconsistent with the catalogs, and results in confusion, which could have been avoided.
After all, when ordering these revolvers, the butt configuration had to be specified - ie, the proper model name. If omitted, the factory wrote back a letter, asking for clarification. I have one such letter, from as late as 1940.
Regards, Mike Priwer