Smith & Wesson did not manufacture and ship firearms in exact serial number order. Frames were often produced in batches, stored in inventory, and then assembled and shipped out over a period of years. This means two guns with serial numbers only a few digits apart could have been shipped years apart.
If you own a rare, historical, or highly valuable S&W revolver, you can request an official Letter of Authenticity. smith and wesson revolver serial numbers database
To find the true serial number, look in these primary locations: Smith & Wesson did not manufacture and ship