hkcavalier,

If there is no letter in front of the serial number you posted such as a C, D, or K (Only with target sights.) then your gun dates to early-mid 1917. If the stocks are original to the gun they will have recessed Gold medallions. The medallions commonly referred to as "Large Medallion" are from the late 1920s to early/mid 1930s and are chrome plated. If your gun has these stocks they are not original to the gun. Stocks from ca. 1920 to 1928 had no medallions at all.

If there is a pre-fix letter then the gun dates to from 1945 to 1982 or so.

In this period 5" barrels are quite common, no rarity at all. As with Muley Gil I find the 5" barrels to be the most aesthetically pleasing and I also own several, both .38 Sp. and .32-20.

The S&W logo has changed sides several times over the years. Some guns even have one on both sides (Often having been back to S&W during the 1960s.) Some, mostly made from 1917-1920, have no logo at all.

The "Made in USA" or later address block, have always been on the lower right front corner of the frame since 1922. This area was unmarked before 1922.

Added:
My one 5" RB M&P is SN 27516x, how close to yours is that? It was used by two Omaha Metropolitan Police detectives from ca. 1918 to 1964 when the department firearms regulations changed to requiring all duty weapons to be 4" .38 Spl. either S&W or Colt. Quite a bunch of old guns got traded in at that time. I have had it since 1964.

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Gunsmithing since 1961