If you want to get really picky, you must make it out of unbleached linen or cotton, hand spun and woven on a hand loom, and sewn entirely by hand, (no sewing machines allowed).

The gillie style shirt has been around a l-o-o-o-ng time, only the details have changed a bit. For warm weather wear when one wants to look more dressed up than in a T shirt, it looks quite good, in my eyes.