You must realize that S&W built guns in "runs". Your gun could be part of a 1,000 gun run. Lets just assume that they were manufactured and assembled in serial number sequence.
Today, guns S 150,000 through S 150,250 were assembled, boxed and placed in the vault. (And I am only guessing on how many were completed in one day)
The vault is a large caged area in the factory with metal shelving racks. The stockboy takes the cart into the vault and places these newly assembled guns on the open shelf where this model is to be stored. He piles the boxes on the back of the shelf and continues stacking them while he works toward the top and front of the shelf.
Tomorrow, the same thing happens, with guns bearing higher serial numbers and the boxes are placed in front of the guns stacked yesterday. This procedure continues until the complete run is stored.
A week, a month, or several months later, a shipping clerk enters the vault to pick a gun, 5 guns or 100 guns to fill an order. He grabs the guns in front and ships them out.
S&W records the serial numbers for inventory control but cares not that the guns shipping out today have serial numbers higher than those on the back of the shelf.
The last gun on the shelf just happens to be the first one assembled by serial number but turns out to get a shipping date 3 years later as it took three years to empty the shelf.
If other runs were made in the meantime as the stock on the shelf was running down, subsequently those guns could end up on the shelf in front of ones made 5 years earlier and so on and so on.
I am not saying that this is a definite process for all guns shipped by S&W but offer it as a possible explanation as to why mfg. dates and shipping dates and pre models and model numbered guns are shipped all over the place.
S&W was in the business to make and sell guns to make money. The only folks that get anal about serial numbers and dates are we collector/accumulators.
