[Ron Wood]

Ron,
A similar question was posed by Big Norm in the thread on the "1913 Commercial". I posted the following there:

"Only the very early 1906 models had the long frame, from about 25100 to 26xxx serial number range with possibly a few scattered above that range. Many of these early '06 long frames will be GESICHERT marked in the lower position and the thought is that they may have been made up from left over '06 Navy frames. After DWM started cranking out 9mm 1906 pieces, all the '06s thereafter pretty much had the short frame".

All 1906 models will have the coil mainspring.

The 1903/04 transitional model, in the approximate serial number range of 25000 to 25100, incorporated the improved breechblock and extractor and introduced the flat toggle knobs rather than dished. However it retained the flat mainspring and togglelock. The change over from the flat spring to the coil spring (1900 Model to 1906 Model) occurred around serial number 25100.