the "transition" of features is pretty well documented, and at least occasionally observed on the 32 and terrier.
here is a "last pre-flat" sculpted latch matched up with the small service grips (rounded field/coarse checker) on a terrier:
and even "last pre-flat latch" paired up with magnas (on a 32):
but i have just never seen any transition of features on the chiefs. i think all the early ones had the "last pre flat" sculpted latch with the rounded corner/coarse checker grips up until number 90, then switched to the oval flat latch and the short magnas at number 91.
this is just my conjecture! from a few years of diligent research, and rabid interest! if anyone has a concrete example of any transitional "grey area" on the chiefs, i would definitely appreciate info!
man, i love these things, and honestly find the early post-war transition of features to be extremely interesting.
The I frames; .22/32, .32 and .38 S&W thumblatches have a completely different evolution than the J frame Chief Spl.
The I frames used four different latches starting with left over pre war latches followed by three different standard type latches ending with the final style which was the same as the first 90 or so Baby Js had. Then c. late 1952 to c. early 1953 (production dates, not shipping dates) the I frames began using the flat latches (starting withe the 2nd style) which continued thru the new Model of 1953 until 1966.
Standard post war (non- flat latch) thumbpieces:
Pre war thumbpieces carried over on the earliest of the post war I, K & N frames; the double hourglass or double 'pinch' around screw hole thumbpiece with relief cuts under checkered pad shown here same as on pre war and very early post war K frames.
2nd style, and first ‘new’ post war thumbpiece, still has the double 'pinch' but without relief cuts under checkered pad.
The 3rd style was a single hourglass with a single 'pinch' in front of the screw hole like a #2 and from the center of the screw to the rear it's like a #4.
4th style which was also the first style used on the first 90 or so Chief Special 'Baby J' frames and last style I frame latch immediately prior to the flat latches. The 4th style was re-introduced on I and J frames after '66 for several years in both blue and stainless until the modern style took over with the lower half shaved off. When the 'classics series' was produced an exact copy of the pre-war style was introduced on them but was an MIM cast part.
On the I frames these four styles were followed by the 2nd and 3rd style flat latch. The 1st style FL was only used on the Baby J frames and airweight K frames.
The flat style usage after the Model of 1953 up dates were the same for all I and J frames.
I & J frame flat latches:
Earliest style Chief latch, ar15ed's #90:
1st style flat latch on this Baby J frame.
2nd style flat latch began on the I frames and Baby Js just prior to the Models of 1953
3rd style on this Pre-36.
Difference between 2nd Flat Latch (on left) and 3rd Flat latch (on right), top view.
http://smith-wessonforum.com/s-w-ha...07291-lowest-chief-special-serial-number.html