You might be able to date it based on this information and the changes that have occurred......
"The Smith & Wesson Model 10, previously known as the Smith & Wesson Military & Police, and for those produced during World War II, the Smith & Wesson Victory Model, is a .38-caliber, six-shot handgun initially developed in 1899 as the Smith & Wesson .38 Hand Ejector model. This model in all its incarnations has been in production since 1899.
The .38 Military and Police Model 10 has historically been the mainstay of the Smith & Wesson Company, with some 6,000,000 of this general type produced to date. It has been described as the most successful handgun of all time, and the most popular centerfire revolver of the 20th Century."
The original Military & Police Model of 1899 was built around the .38 S&W Special round--a slightly elongated improvement on the .38 Long Colt with increased bullet weight (158 grains) and increase in powder charge from eighteen to twenty-one grains of black powder. The round's full name is actually .38 S&W Special. A number of the first models were chambered for .38 Long Colt to satisfy a government order. Serial numbers ranged from number 1 in the series to 20,975 at which point (1902), the model underwent substantial changes., in particular the S&W Military & Police Model of 1905 (mfg 1905 - 1942) chambered in .38 Special.
Changes include major modification and simplification of the internal lockwork and addition of a barrel- mounted locking lug to engage the here-to-fore free standing ejector rod. The 4th change of April 20, 1915 had enlarged service sights that quickly became a standard across the service revolver segment of the industry. Heat treating of cylinders began in 1919.
The first model M&P of 1899. The ejector rod is free-standing lacking the front barrel latch of later models
The lockwork of the first model differed substantially from subsequent versions. Note that the trigger return spring is a flat leaf rather than a coil spring powered slide, unlike the variations dating from 1905 onwards.
The M&P 1905 fourth change of 1915. The lock mechanism remained principally unchanged after this model.The Model 10 is a fixed-sight revolver with a fluted cylinder. Over its long production run it has been available with barrel lengths of 4 in. (102 mm), 5 in. (125 mm), 6 in (152 mm), 2 in (51 mm) and 3 in (76 mm). 2.5" barrels are also known to have been made for special contracts.
At present (2007) the Model 10 is available only in a 4" (102mm) barrel model. The Model 10's stainless steel (Inox) counterpart, the Smith & Wesson Model 64, is available in either a 4" (102 mm) or a 3" (76 mm) barrel.
The S&W Model 10 military revolvers produced from 1940 to 1945 had serial numbers with a "V" prefix, and were known as the Smith & Wesson Victory Model. It is noteworthy that early Victory Models did not always have the V prefix. During World War II, huge numbers - over 570,000 - of these pistols, chambered in the British .38/200 caliber already in use in the Enfield No 2 Mk I Revolver and the Webley Mk IV Revolver, were supplied to the United Kingdom, Canada, Australia, New Zealand, and South Africa under the Lend-Lease program. Most Victory Models sent to Britain were fitted with 4" (102 mm) or 5" (127 mm) barrels, though a few early versions had 6" (150 mm) barrels. In general, most British and Commonwealth forces expressed a preference for the .38/200 Smith & Wesson over their standard Enfield revolver.
The Victory Model was also used by United States forces during WWII, being chambered in the well-known and popular .38 Special cartridge. The Victory Model was a standard-issue sidearm for US Navy and Marine aircrews, and was also used by guards at factories and defense installations throughout the United States during the war. Some of these revolvers remained in service well into the 1990s with units of the US Armed Forces, including the Coast Guard. Some Lend-Lease Victory Model revolvers originally chambered for the British .38/200 were returned to the U.S. and rechambered to fire the more popular and more powerful .38 Special ammunition, and such revolvers are usually so marked on their barrels. Rechambering of .38-200 cylinders to .38 Special results in oversized chambers which may cause problems.
The finish on Victory Models is typically a sandblasted and parkerized finish, which is noticeably different from the higher-quality blue or nickel/chrome finishes usually found on commercial M&P/Model 10 revolvers. Other distinguishing features of the Victory Model revolver are the lanyard loop at the bottom of the grip frame, and the use of smooth (rather than checkered) walnut grip panels. However some early models did use a checkered grip. Most notably the pre-1942 manufacture.
World War II models
After World War II ended, Smith and Wesson returned to manufacturing the M&P series. Along with cosmetic changes and replacement of the frame fitting grip with the Magna stocks, the spring-loaded hammer block safety gave way to a cam-actuated hammer block that rode in a channel in the side plate (Smith 1968). In 1957, Smith and Wesson began a convention of using numeric designations to distinguish their various models of handguns. The M&P was renamed the Model 10.
The M&P/Model 10 has been available in both blued steel finish and nickel finish for most of its production run. The model has also been offered throughout the years with both the round butt and square butt (i.e. grip patterns). Beginning with the Model 10-5 series in the late 1960s, the tapered barrel and its trademark 'half moon' front sight (as shown in the illustrations on this page) were replaced by a straight bull barrel and a sloped milled ramp front sight. Late model Model 10s are capable of handling any .38 Special cartridge produced today up to and including +P+ rounds.
As its name suggests, the S&W Military & Police revolver was developed for military and police use. In this regard it has been enormously successful, with the Model 10 remaining in production today. The Model 10 has also enjoyed popularity with civilian shooters in countries that allow private ownership of handguns.