I ordered a new recoil spring from Numrich Gun Parts (e-gunparts.com) and it arrived in a non-decript plastic bag without any "genuine" S&W part designation. Should I use it or order another direct from S&W? It fit in the gun well and my old spring was about 3/4" shorter so I think it needs replacement.

There are lots of manufacturers for replacement springs. My 2 cents is if fits and works and you've already paid for it...use it. Next time you think you need replacement springs, maybe order directly from S&W...but I would venture a guess the spring you have now will work fine....

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Model 36, 39-2

i get all my replacement springs from wolf spings, they are better and better priced.

Small parts orders (like springs) from S&W are usually shipped in plain plastic zip lock bags, usually with a part number written on it, sometimes not, but nothing is on them to identify them as "genuine" S&W parts.

I've received many parts that way ordered through S&W customer service.

The only time I've seen something in packaging marked "genuine", was a replacement or accessory parts (grips, rear sight blades, target hammer/triggers) for sale by retailers.

I don't care too much for Numrich anymore, they've become too much of a "hit & miss" proposition when it comes to getting the part that you thought you were ordering based on what they had in the part description.

I've had mixed results with Numrich-

I've ordered replacement Novak Sights and Recoil springs for a 5906, 6906 and 3913 - no problem. Then I ordered 3 firing pin springs for all three (they are the same part for all three pistols). I received 3 springs, 2 of which were longer than the 3rd. The 2 longer springs were definitely not the right part. When I contacted Numrich they sent 2 more springs - and they were still the wrong part.

Next time I go to Wolff or S&W.