If you want a much more detailed explanation you’ll find one here.
On to the quick and easy version…
Round seal on the front of the box is OLDER than the oval seal.
Colors of seals does not mean anything.
Rev-A (bottom right corner on the front of the box) is NEWER than boxes without Rev-A.
5-screws on the back of cartridges are OLDER than 3-screws.
Boxes with perforated punch outs for a fold up hang tab on the back of the box are OLDER than boxes without that built-in hang tab.
Ignore stuck on plastic hang tabs in determining age, they aren’t significant.
Those are 4 quick to spot keys to understanding earlier vs later in boxes and cartridges.
Getting a bit more into the weeds but for a very important determination…
If there is a round sticker at the top of the box you have a VERY early version of an NES Black Box game, again more here, with a very subtle difference in 1st or 2nd (dependent on the game, because nothing is that simple) variant of the game.
If the sticker is a dull finish with word Nintendo in the middle of it (often tough to see when the game has been opened carefully) it is what is referred to as a matte sticker version and this is a test market copy of the first 17 titles released by Nintendo – very rare, and almost impossible to find still sealed.
If the sticker is a bit shiny, that’s referred to as a gloss sticker version and is the second print of the original 17 releases and a first print of the second 10 games released. The word Nintendo is still on the sticker and if removed this sticker leaves the words VOID behind on the box.
Of course there are exceptions and oddities here and there but this article was titled quick and easy guide to NES games.