The nickle plated Model 39-2s have the same parts blued as you describe. I wouldn't doubt that you have a nickeled pistol. Not all 39-2s have the red plastic insert in the front sight: it's a nice touch.

Edited to add: S&W magazines are stamped S&W, and sometimes the caliber, on the bottom of the floorplate. All except one: I have a 39 magazine where apparently the floorplate went through the machine upside down, and as a result, it's stamped on the inside instead of the outside.