Insignia Stacking Verification; Nightstalkers Insignia for Assassin.

Nightstalker's Insignia Armor +15 (while attacking)

Does this stack?
Would you be able to secure one in each of your armor pieces like say, attunement//survivors for a total of +75 armor while attacking?

No it doesn't stack. The +15 armor applies only to the piece you stick it on.

It doesn't stack. If you only put that insignia in your chest piece then you will only have +15 armor when you are hit on your chest piece(and are attacking ofcourse).

Guild Wars uses a "hit location" system when it comes to armor and the damage reduction that armor offers. Like if you get hit in the chest, only your chest armor and the bonuses on it are taken into account.

So while you can put a Nightstalker insignia on all five pieces of armor that you're wearing, only one of them is going to be taken into account when you get hit by an incoming attack.

Okay, that's what I wanted to know, thanks.