Bob,
Great Baby J, 2nd version pick up, especially with smooth front sight. It has the 2nd style latch for the Chiefs Spl which of course is the FIRST style flat latch; it is slightly ramped to the front as you described. With a slight convex surface.
POST WAR THUMB PIECES, IN GENERAL
1. All pre war thumb pieces are the same styles in two sizes: I frame and K/N frame.
2. Post war I frames and the J frames thumb pieces have many variations:
A. four ‘standard’ styles used on I frames, (two on K/N), but only the 4th style was used on the J frames, and only up to ~ s/n 117 on the baby J frames.
B. 3 ‘flat latch’ styles used on J frames (and M&P K frame Airweights only), and only the 2nd and 3rd styles on I frames.
On all early post WWII Transitional Models including I frame .22/32s, .32s and .38/32s you will find the beautifully sculptured pre-war latches, along with medium ejector rod heads (not mushroom), and even flat silver grip medallions on occasion. And you'll find them out of sequence with serial number advancement and/or gun delivery dates; no surprise to most of us.
On later post war guns, '49 and early '50s, you'll find a slightly sculpted but more blocky style, with no undercutting of the top and bottom flared edges (very few of these). And then the most common up to ‘52-‘53 is the standard blocky type used on all size frames from '66 thru the 90's.
The three styles above tend to coincide with other changes like ramped front sight with barrel rib and leaf mainspring change to coil spring that precede the change to the Improved I frame.
The flat latches began in 1950 with the #1 style on the then brand new Chief's Spl in .38 Special above ~#117. First on the 1/8" longer 'baby J' frame 5 screw, with rounder I-frame-type trigger guard and short butt, continuing on the Chief thru the change in 1953 to the 4 screw standard J frame with egg shape trigger guard, longer round butt and longer still, new style square grip frame, with three consecutive distinctive styles of flat latches 'til 1966.
Flat latches for .22/32 Kit Guns coincide with the change started with the Model of 1953, to the 4 screw New I frame (again, egg shape T. Guard, longer round grip and even longer square grip frame) .22/32 Kit Gun (4") and Target (6"). The .32 and .38 S&W guns got the flat latch around the same time but while still pre-war style I frames, with both flat mainspring, coil spring change and then the conversion to the New I frames, (progressing thru the 3 flat styles); thru the 4 screw to 3 screw change, and the model number commencement in '57. In 1961 all three were built on the 1/8" longer J frame like the Chief's Spl in .38 Special and given -1 model numbers. But the flat latches followed these four guns thru 1966 when the 'experiment' finally ended. The '50s transition models make for a boat load of collectible small frame guns!
USE OF FLAT LATCHES
The 1st style flat latch began exclusively on the Baby J after ~ #117. The only other model the 1st style was used on was the alloy K frame, never on the I frames.
The I frames used all four styles of the standard thumb piece before beginning use of the flat latch, starting with the 2nd style on the Improved I frame - 2nd Variation (ramp sight and barrel rib) in 1953: above # 60430X on the .32s, at around # 747XX on the .38 S&W.
There are no Improved I frame .22/32s neither 1st or 2nd Variations; so for the 22/32s, the coil spring and 2nd style flat latch began with the Model of 1953 New I frames.
The Baby J frame in the high 26,000 range, began a transition to the 2nd style flat latch also in 1953.
So all Models of 1953 New I frames and New J frames were introduced using the 2nd style flat latch. A transition to the 3rd style flat latch began in the late 1956 period for all I and J frames until discontinued on all models in 1966.
THREE STYLES OF FLAT LATCHES:
1st style flat latch used only on the Baby J frame and K frame airweights.
Photo by jackvs1
2nd style flat latch began on the I frames, Baby Js and K frame airweights just prior to the Models of 1953.
3rd style shown with steeper incline at the front, on lower .38 Chief Spl. in first photo and in 2nd photo; used on I, full size J frames, and K frame Airweights beginning mid late ‘50s; ending in 1966.
FOUR I FRAME ‘STANDARD’ STYLES OF THUMB PIECES USED POST WAR THAT PRECEDE THE FLAT LATCHES:
The four I frame thumb pieces of the .22/32, .32 and .38/32 prior to the introduction of the flat latches, have a completely different evolution than all other frame sizes. And you'll find them out of sequence with serial number advancement and/or gun delivery dates; no surprise to most of us.
These post war revolvers used four different thumb pieces prior to the flat latches starting with left over pre war thumb pieces followed by three different and new standard type thumb pieces ending with the final style, which is the same as the only style used on the first ~117 J frames (Baby Js). Used from 1946 to c. early 1953 (production dates, not shipping dates).
The 1st thumb piece used post war; left over pre war thumb pieces, carried over on the very earliest of the post war ‘Transitional’ I, (also K & N) frames; the ‘double hourglass’ or ‘double pinch' around screw hole thumbpiece with relief cuts/flare under checkered pad shown, off and on a K22/40.
(Note: When the modern 'Classics Series' was introduced, an exact copy of this #1 pre-war style old inventory transitional post war style was introduced on them but is an MIM cast part.)
Photo by RKmesa
Flared or relieved edge:
(photo by JP@AK)
2nd style used, and first ‘new design' post war style thumb piece, still has the double 'pinch' but without relief cuts under checkered pad.
Flat edge (photo by JP@AK):
The 3rd style used (2nd new post war style) was a single hourglass or single 'pinch' in front of the screw hole like a #1 & 2 but from the center of the screw to the rear it's like a #4 below. Only seen on I frames.
4th style used (3rd new post war style) with no ‘pinches’ ended on the I frames with the introduction of the 2nd style ‘flat latch’, just prior to the Models of 1953. It was the style used on the first 117 or so .38 Chiefs Special Model of 1950 'Baby J' frames followed by the #1 style ‘flat latch’. This 4th style was used on all K and N frames immediately following the left over #1 pre war style just prior to the Models of 1950.
The 4th style was re-introduced on all I, J and K frame Airweights in 1966 and used for several years until the modern style with shaved off lower half took over ~ 1995-96.
