I'm not sure about that either. I just brought up the Guerlain twin-G logo because, in addition to the gold cap, it's another way to feel confident that you have the best formulation. I also brought it up because most of us are going to be looking for "vintage" Heritage bottles on eBay. But you see all kinds of things on eBay and it can get confusing.
Here's an example of a bottle of Heritage EdT that has everything you look for. First of all, I believe that's the original box, it's sold by a reputable seller, it has the gold cap, it has the Guerlain insignia above EdT, and it's specifically advertised as "Vintage".
https://www.ebay.com/itm/HERITAGE-de...wAAOSwYKZfVXuT
But then look at this odd example: This is a bottle of Heritage with a gold cap, but it's EdP, not EdT. But notice that even though it has the gold cap, it doesn't have the Guerlain insignia on either the bottle or box. And it's being sold by Fragrancenet. So is this the original formulation, or not? I really don't know. I do know that I have the original EdP and it DOES have the Guerlain insignia on the bottle. (I suppose the picture here could also simply be incorrect.)
https://www.ebay.com/itm/Heritage-by...wAAOSwCU1Y07P3
And then you have this one: Someone decanting what they advertise as "vintage" Heritage when it has the silver cap, there is no insignia, and Heritage is above EdT....so it's obviously not "vintage". Don't know if they are intentionally being deceitful or if they don't know what's vintage.
https://www.ebay.com/itm/Vintage-Gue...QAAOSwOopf4i8e
Another reason to look for the Guerlain insignia is you might run across a tester bottle of Heritage without the cap. But if you see the Guerlain Twin-G logo on the bottle, that's an indication that it's the formulation you're looking for.