Help me learn more about this S&W single-shot transition pistol (2nd-to-3rd model)

[Updated August 14, 2017: I am reviving this thread to renew my search for documentation on any 3rd Model Single Shot (i.e., double-action Single Shot) with a serial number lower than no. 4007. I have also repaired the damage done to this thread when Photobucket recently disabled all the photo hotlinks.]

Our subject is a Smith & Wesson single-shot target pistol, serial number 4007, shipped February 11, 1910. The number 4007 appears everywhere it should – on the grip-frame, barrel flat, clasp, and ejector plate. No. 4007 has been designated as a 3rd Model Single Shot "transition variation," for reasons discussed below. I would like to learn whether anyone out there has a 3rd Model Single Shot (i.e., a Single Shot with the double-action clockwork) that has a lower serial number than this.



SOME BASIC BACKGROUND INFO

A little background info for those not already well versed in the S&W single shots: There were four models of S&W single shot target pistols. The 1st Model, produced 1893-1905, was a single-action pistol, an offshoot of the .38 Single-Action 3rd Model revolver. The early 1st Model single shots had recoil shields and other carryover attributes from the revolver, although these revolver attributes fell away as the 2nd Model evolved into a dedicated single-shot design (late 1st Models typically lack the recoil shield, for example).

The 2nd Model single-shot was produced 1905-1909. It too was a single-action pistol, generally similar in outward appearance to the 1st Model, but without the recoil shield or other revolver attributes.

The 3rd Model single shot, manufactured 1909-1923, incorporated a different action, adopted from the .38 Double Action Perfected Model revolver, allowing operation in either single or double action. It differed from the 2nd Model in other respects as well, some of which are discussed below.

The 4th Model, the "Straight Line," produced from 1925-1936, was of an entirely different design. The 1st Model and 4th Model are not further discussed in this post, because this post is concerned with the transition from 2nd Model (single action) to 3rd Model (double action) pistols.

The 2nd Model began a new serial number series, and the 3rd Model continued in the same series. Various references give the 2nd Model serial number range as being 1-4617 (for example, Smith & Wesson 1857-1945 by Robert J. Neal and Roy G. Jinks, 1966, 1975), p. 38. I own 2nd Model no. 767 (1906), and I have a 2013 factory letter on that pistol. The letter implies that the serial number range for the 2nd Model goes to 4617 ("a total production of 4617").

For the 3rd Model, the Neal-Jinks book gives the serial number range as 4,618 to 11,641. Moreover, I have a 2010 factory letter on a 3rd Model (no. 7778) in which Mr. Jinks wrote, "These [3rd Model] pistols were manufactured in the same serial number range as the Second Model Single Shot and are numbered between serial 4618 and 11641."

But notably, the standard language in factory letters on 3rd Model pistols more recently changed. In a 2013 factory letter that I obtained on 3rd Model single shot no. 8871, Mr. Jinks wrote, "These [Third Model] pistols were manufactured in the same serial range as the Second Model Single Shot and are numbered between serial 4000 and 11641." [italics added for emphasis]

So then -- were pistols in the 4000 to 4617 range 2nd Models, or 3rd Models, or hybrid transition guns, or some of each? My tentative conclusion is that most of the pistols in this serial number range were single-action 2nd Models -- but some were transition guns that incorporated double-action clockwork, which will letter as 3rd Models. Regarding these "transition variation" 3rd Models, no. 4007 is the lowest serial number I've yet encountered or seen documentation on.

At this point I am going to insert a number of photos that will help illustrate some of the external differences between an early 2nd Model (no. 767, 1906) and a fairly early 3rd Model (no. 8871, 1919), and show how the transition variaton pistol no. 4007 incorporates elements of each. (All three of these pistols have matching numbered parts, and all three are chambered in .22 LR.)

COMPARING 2nd MODEL, TRANSITION PISTOL NO. 4007, and 3rd MODEL

The 2nd Model's single action is immediately evident to casual observation by the position of the trigger near the rear of the trigger guard. In contrast, on the 3rd Model, the trigger rests centered in the trigger guard, as typical of double-action handguns. Here are the three guns in one photo -- top to bottom: 2nd Model no. 767 (shipped 1909), transition pistol no. 4007 (shipped February 1910), 3rd Model 8871 (shipped 1919).



The frame-plate of the 2nd model, giving access to the single-action clockwork, is on the left side of the frame (top photo). The frame-plate for the 3rd model, giving access to the double-action clockwork, is on the right side of the frame (bottom photo).





The transition pistol has the frame-plate on the right, as on the standard 3rd Models.



Barrels made for the 1st and 2nd Model had a convex lug on the bottom, that fit into a concave recess on the frame.



In contrast, the 3rd Model barrels had a flat bottom, with a flat frame to match. Therefore, barrels made for the 1st/2nd Model will not fit on a 3rd Model unless gunsmithing is done to mill flat and shorten the barrel lug.



Notably, the transition pistol no. 4007 retains the convex lug-concave recess attributes of the 2nd Model.



Barrels stamped "Model of '91" were originally made for the 1st Model, and were also used on many 2nd Models, including my no. 767 (top photo). Later, additional barrels were made for the 2nd Model with a one-line barrel address with no patent dates, and the transition pistol no. 4007 wears one of these (see middle photo). The 3rd Models typically had a two-line address, such as shown here on no. 8871 (bottom photo).







The 2nd Model rear sight was held by two screws facing the shooter -- it was adjustable for windage after a fashion, although with difficulty (top photo). (Note: this particular sight blade is, I believe, not original.) The 3rd Model had a more sophisticated rear sight design that allowed windage adjustment by manipulation of screws on the left and right of the sight leaf (bottom photo). The transition pistol no. 4007 has the 2nd Model rear sight design (middle photo).







The 1st and 2nd model pistols typically wore black hard-rubber stocks, while the 3rd Model had walnut extension-type stocks. As seen in the photos above, the transition pistol no. 4007 wears the 2nd Model style, black hard rubber stocks. The transition pistol stocks are not numbered, but a previous owner engraved his name inside the right panel, a long time ago, judging by the appearance.



QUESTIONS

Can anybody provide information on any S&W single shot, with all-matching numbers, with the double-action mechanism, that has a serial number LOWER than 4007? I would like to entertain the possibility that this pistol is a prototype for the double-action 3rd Model.

Beyond that, I would be very interested in any information on the attributes of other single shots that fall within the transition-zone of 4000 to 4617.

Thank you!