In wine, which carries with it the only actual meaning of "vintage", it's simply the product of a particular vineyard in a season.
Hence, the "vin" which means "vine" and where the word wine comes from.
And it
always refers to a specific year, well, more accurately, a specific growing season. There may be better years than others for particular grapes, vineyards, regions, blends and growers, but the term "vintage" doesn't mean anything regarding that. There is no association with quality in the strict sense of the word's meaning, since every single grape is part of a vintage somewhere somehow. If it's a better grape that leads to a better wine is up to you to know.
Of course, in wine sales as well as guitar sales and the rest of it, "vintage" has come to mean quality in an effort to make sense to people who don't really know what they are buying in an effort to separate them from their money. "It's vintage!"
But, really, when it comes to guitars and cars and literally everything else it's bullshit. It's been corrupted to mean things that are old, or collectible, and that's also prevalent with wine also. But that shit you have in a box from California has a vintage as does the best champagne* you ever hoped to pour on a bunch of hookers once your rap career takes off.
And I know that there are now legal definitions of "vintage" that refer to cars after a certain age. It's still bullshit. The word doesn't mean that. Use "collectible" or something.
*Strictly speaking most champagnes are not from a specific vintage. They are usually blends from various vintages. That's why you don't see a date on there. There are now, though, grower's champagnes which are pretty cool, and they vary a lot from year to year, as you'd expect from a wine that has an actual vintage.
https://en.wikipedia.org/wiki/Grower_Champagne" onclick="window.open(this.href);return false;
Back in those days, everyone knew that if you were talking about Destiny's Child, you were talking about Beyonce, LaTavia, LeToya, and Larry.