Sample 1:

Possibly prototype of removable plate bags that did not make it into the final Aircrew Endurance vest.  Has hand-written labeling like other modern prototype/test items.  CMU-37 is for crew and CMU-38 is for (co)pilot (source: http://www.usmilitariaforum.com/forums/index.php?/topic/330974-cmu-37-and-38-prototype-body-armor-pouches/).

Final Aircrew Endurance Vest: