So...I submit this to the judges....

My dad just presented me with a nickel Model 40 (marked as such, not a "pre"). Serial number 16166.

So here is my question: the S&W Bible states the 4th screw was eliminated in 1955. This is obviously a later gun as it possesses a model number...but also a 4th screw.

Can I assume that Smith was just blowing out parts that were left over?

There is a similar 40 on Gun Broker in the 14000 range that letters to 1959
I know there is often no rhyme or reason to the non-sequential nature of Smith serial numbers....but what gives?

Did they really have several years of backlogged parts?

I am guessing this is the case as I also have an Airweight Centennial with a bug screw...that is marked Model 42. Probably a first year production gun that hung around for a while.

Just Tuesday night musings....

I'm certainly not an expert but I own a model 14 no dash from 1959 which is also a 4 screw. Seems to me the model numbers with no dash are 4 screw guns the dash 1 signifies screw delete.

It get worse. 4 screws number into the 21,000s.

Is it safe to say this is an early '60's gun then?

Probably. However, the .38 Centennial/model 40 was not a popular gun during its initial production run, so the times it was made and sold may differ by several years. A letter of authenticity is the only reliable way to find out the latter, called the "ship date":

Smith & Wesson Historical Foundation - Letter Process - Insuring that the rich history of Smith & Wesson will continue for generations to come

__________________
Alan
SWCA LM 2023, SWHF 220