iPhone 4 with serial no 7S

I don't, but some time ago someone posted that phones beginning with 7 or 5 are refurbished. I do not know if they were correct or not.

I know the first two numbers are supposed to be the factory they were made in. All mine have been in the 80's (82, 83, 84, and 86, I think).

The 4th and 5th spots in the number are supposed to be the week of manufacture (from the start of the year). Mine is week 37. I think they are at at least 40 for the newest phones now. Maybe 41, though that doesn't mean all the older ones are sold yet. If your phone is a replacement for one you returned, it could be refurbished, especially if the 4th and 5th digits go back very far. My first phone, bought about July 11th, was week 22.

Well, if it's week 39, it's less likely to be refurbished and if you haven't bought it, we aren't talking about a replacement phone anyway. No phone bought originally should be refurbished.

Well, if nothing else your report seems to kill the idea that a "7" at the start means a refurbished phone!

I never heard anything about a 7S being better. Nothing at all about that.

Is this from Apple or are you buying it from someone else? If from someone else, has the box been opened? If so, then that changes things a lot. They could have put a different phone in the box (which brings back the possibility of it being refurbished). Could even be a knock-off rather than a real phone. Or stolen. All kinds of possibilities.

Factory/Machine ID that starts with 7 are actually made by Apple's factory lines, while those starting with 8 are made in China. They can be 79, 7R, 7S, 7T, 7U, or 7V.

I'd avoid the reseller and buy from a legitimate authorized source.

There is no guarantee that any particular week/serial number is better than any other week.

All iPhones are made by factories in China for Apple.