The belts are used for several other models ,so probably manufactured recently
the Gates I recently purchased doesn't look "old"
obviously ,like tyres etc ,there is "new old stock" being sold too
I wonder if the belt is only used on GM V6s? The Renault 24v V6 cam drive is
very similar for instance. That would make recently manufactured parts more likely.
I've had some bad experiences with genuine NOS rubber parts like hoses, belts and seals and now my preference is for up to date stock whenever possible. One forty year-old genuine Girling master cylinder(for a single circuit, non-servo Avenger, so a very limited use part
) bought from a specialist supplier was supplied with the advice "it comes with a pack of new seals, and we strongly recommend you use them".