I have never purchased a firearm that arrived in a seal.

Though, when dealing with a local FFL several years ago, I field-stripped a pistol before accepting the transfer and the FFL said, "no one has ever inspected a pistol like that". Seemed odd to me she did not find it to be a common practice-- you wouldn't drive off the lot in your new car without at least kicking the tires, right?

Regardless, all S&W mags that shipped with pistols have what appears to be black crayon that someone marked across the top of the follower.

Upon cleaning a new pistol of S&W tier, you will discover most all components are dirty-- pistols of this class are factory fired. I recall hearing this was a law(?). If a yellow-like substance shows up on patches during your initial cleaning, that is a factory protectant. Also, the ammo they use is probably bottom of the rung, filthy dirty stuff.

I would agree with the notion of contacting the seller and being upfront about your concerns, see what comes of that conversation.

Otherwise load it up and put some lead through it, assuming there are no functionality issues, rest easy-- it is ultimately a tool and function is key, people buy new pistols that fail to function, and that.. that sucks.