OTV, IOTV, MTV and everything all the way back to the beginning of firearms.  Someone have a link?  Maybe we can learn something.

what are you looking for?

Here's a good read to start

http://looserounds.com/2014/11/10/body-armor-vietnam-use-and-development/

This little book gives a good overview:

http://www.amazon.com/Flak-Jackets-Twentieth-Century-Military/dp/0850455693

This article covers quick history of Body Armor with Army SF



Defense Review SOF Top gear pics

Here's the story behind the term bullet proof:

Back when plate armor was in use, black smiths would test examples of their armor. They'd see how many blows it could take from a sword, an axe, crossbow, broad head arrows, bodkin arrows, et cetera. If they passed the test, then they would rated or proofed for that.

Some examples of armor had testing done with early guns (no idea on the parameters), but the armor tested stopped the bullet. Hence, it was bullet proof.