Centennial Airweight/Model 42 - when did the thumbpiece and grips change?

[ThePenultimateNinja]

I'm trying to find out some information on the history of the Centennial Airweight/Model 42.


The original grips on the Centennial Airweight were smooth wood, and the thumbpiece was a wedge-shaped flat type.


At some point, these were changed to the Magna grips with the checkered panels, and the familiar 'dished' thumbpiece that was found on other S&W revolvers from that time period.


I know the Centennial Airweight was renamed to the Model 42 in 1957; is that also when the grips and thumbpiece were changed?


Also, when was the grip safety deleted?


Thanks in advance