This is like a scapular I got at my First Communion. It's not an article of clothing it's like an I.D. tag one hangs in front and one in back......more like a necklace type thing.
More,
A friend of mine wore one of those and if I remember correct, among other things, if wearing one and you die, you get to go to the express line so to speak to heaven. I know that's probably way over simplified and there are other reasons involved but in a general sense that was one potential aspect of it. Is that kinda close to being a bit right?
In fact, his looked almost identical to the pic you posted and it was the mid-80's when I saw it but I still remember that pretty green on that white cloth. Really stood out.