FS Smith & Wesson 357 magnum blued 4 inch serial AUV83689

[1991bigmac]

its marked 357 magnum on the barrel

 

[Wheeler]

Take a look on the frame when you open the cylinder. The Model number is stamped there. It's quite possible that it's a M27 with an incorrectly stamped frame. A call to S&W with the serial number can get that question answered quickly.