Vin + Age;
Vin = Wine, Age of course is how old. That's Vintage. It can be this years Vintage or it could be a century old Vintage or any other year.

As relates to shotguns Vintage is most often MIS-used in an effort to increase prices.

Age for vintage is relevant only when the Vintage is specified as in;

A Committee of Safety Musket is of the Revolutionary War Vintage while an M-16 is of the Vietnam Vintage.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra