Welcome to the Forum! You've inherited a very nice post WWII M&P .38 Special, and it should be a great family heirloom to pass down for generations to come! There were millions of M&P revolvers manufactured by S&W over many decades, so your revolver is not particularly rare or valuable. The "old timer" was correct, yours is a 5-screw K-frame revolver (4 screws in the right side plate and one in front of the trigger guard). The upper plate screw was discontinued in 1955 and they became 4-screws, and the M&P became the "Model 10" when S&W started model numbers in 1957. The M&Ps are extremely reliable and accurate revolvers, and yours looks to be in VG condition. The walnut stocks (grips) are also in excellent shape. Hopefully you'll take it to the range and shoot it from time to time. Enjoy!