Howdy
Given that the SCSW does not break down serial numbers for the 38 M&P 4th change beyond the broad range of 1915 through 1942 it can be a little bit tough to pin down the date a particular revolver was made. Also, bear in mind that all the information Roy Jinks, the official S&W historian, has on file relates to ship dates, not manufacturing dates. Sometimes guns sat in inventory for a while, they did not always ship according to serial numbers.
Anyway.
This 38 M&P Target Model, SN 2646XX, shipped in 1917. Notice your revolver has the same large, mushroom shaped cap on the end of the ejector rod. I do not know exactly when S&W stopped using that type of cap, but it is a fairly good indicator of age, I am going to guess it was used through the 1920s. This revolver is wearing the correct grips (yeah, I always say grips) with recessed gold medallions that were used about 1910 to about 1920. The grips on your revolver with the flush silver medallions were used about 1929 to about 1941.
This well worn old M&P shipped in 1920. The SN is 3394XX. The very worn walnut round top grips are the type used from about 1920 until 1929 and they are lettered to the gun. Notice it too has the large, mushroom shaped ejector rod cap.
Frankly, the grips on your gun are in such nice shape, if it were mine I would just leave them on it. If I wanted to find a set of the correct grips I would probably place a post in the Want to Buy section of the Smith and Wesson forum. You could also mention it in the post you put in the regular area of the forum. You never know, once a guy sent me some grips for a Victory Model free of charge.
Regarding shooting it without hurting your finger, thousands of officers carried these for many, many years without grip adapters. I don't have grip adapters on any of mine and I shoot them with standard loads all the time. Never get my finger whacked. If you want a grip adapter that is up to you, but I like to keep my old revolvers stock, which means no grip adapters.
Just so you know, S&W began heat treating cylinders for the 4th Change around SN 316648, so no +P loads. Mild factory loads only.
By the way, nice find. I would probably have shelled out $580 for it if it's as nice as it looks in your photo.
Welcome to the S&W Collector addiction.