Take a look in the datasheets, amphenol, neutrik, hicon or switchcraft.
It says "silver" in the datasheet, not "silvery metal".
It looks like silver on the connector.
The tarnish looks like silver.
OK, my bad - then, this is a thing now. I mostly use cheap connectors.
Even heavily "corroded" silver contacts still work fine, even with dynamic microphones that pick up a fart from the fly on the wall.
Of course they work - because audio is not critical. That's how the audiofool business works; you can sell anything as high-tech. They will tarnish, increase contact resistance and possibly cause heavy distortion. But people will be fine. Increased resistance doesn't show up, and if there ever is distortion, people will juggle the connectors or just buy a new cable. No big deal. Getting rid of bad cables and jiggling the contacts is everyday life even in professional audio. Everybody knows the scratching sound of bad contacts. We are just so used to it that we don't complain. It's only a source of nuisance. If it was a real security issue, the connectors would just work. This would mainly happen by physical design, correct plating being secondary. (For example, the XLRs work much better regardless of plating, whereas 1/4" instruments plugs are always a PITA, more or less, but still "ok enough" so we live with them.)
And, to be fair, I
have seen silver-plated connectors - but they have all been a lot older than 20 years, something from the 70's.
But, this thread is kind of theoretically discussing about plating and whether it makes sense to gold plate or not. And to answer that, yes, gold plating really actually makes some sense, it's not merely a marketing trick (as anyone designing a PCB card edge connector knows!). But I guess
silver plating
is a marketing trick, even more than gold plating ever was, because unlike gold plating, silver plating doesn't make sense, or at least I can't see it. I might be wrong.
And, in professional installations, I have only seen nickel and gold - and no tarnish. But I haven't seen much of the scene in the last 10 years or so.