The suit and number style in 4 are probably just an artistic change. We've seen a lot of this already in the designs of creatures and weapons. I would guess that any and all vault suits, barring an easter egg, will be similar. I kinda like it because it more closely resembles the designs from 1-2.

Going to say 17.

Here's more info about vault 17 also if you click the picture icon you get a very large picture to inspect it.

http://fallout.wikia.com/wiki/Vault_17

http://vignette2.wikia.nocookie.net/fallout/images/6/65/Fo4_Vault_17_jumpsuit_concept_art.png/revision/latest?cb=20150617233032

Looking at it closely, it's 17. The 'shadow' is really the outline of the dude's back. I'm not sure what you mean by angle, though. We can clearly see most of the back to determine what the number is.

As Raven said, the "1" is written with the little slant dash on the top, and the "7" is "7". It's a Vault 17 jumpsuit. I guess we meet a Super Mutant/Nightkin who gives this to us?

I don't disagree with the possibility and plausibility of some arguments for vault a 17 jumpsuit.

We have elements of the East Coast Brotherhood of Steel that made it to the West Coast, plus the Enclave also, and, the presence of Super Mutants on the East Coast indicates a migration from the West since the original FEV dipping vats were in the West, the Super Mutants can't procreate, and the vats were destroyed.

It's thus plausible and possible for other things associated with the West side of the continent to wind up on the East side.

Arguments against this, however, also have merit.

The curve of the character's back from shoulder to shoulder in the angle of the source picture, combined with a slight ambiguity of the median vertical line on the characters back give enough wiggle room of ambiguity that the vault could very well read 117.

Additionally, since the game's setting is in the East Coast area, and vaults numbered in the 100s are the fashion for this area in the numbering convention established, there's substantial merit for a higher plausibility and probability for the jumpsuit to be a 117 jumpsuit.

There are additional arguments for both 17, and 117, such as 17 goods and material collected by wasteland scavengers who found the vault in the West making it's way into the Brahmin trader network and creeping from coast to coast, hand to hand, or meeting a former 17 resident that didn't grow so big during mutation as to rip the suit to shreds, that might even be available as a human/ghoul sized super mutant companion, potentially even with senses intact, and potentially available to use all the human and ghoul sized armors.

Occam's Razor is a little indifferent too. It looks like it reads 17, so it must be 17 ... or, 117 is East Coast, the game is on East Coast thereby 117.

Unless there's other concept art, in game footage, and/or something else that comes out of Bethesda that confirms one of these, it's likely we won't know for sure until we get our grubby mittens on the actual game.