Just picked this up today at a thrift shop in Northern VA! I would imagine the experimental t-shirts are a little harder to find considering more people would likly keep a uniform versus an undershirt... Looks brand new too!
According to the trials pictures they fielded 4 types:
Performance T = polyester Cotton T = obvious
Performance Mock Turtleneck = polyester with thick collar Cotton Mock Turtleneck = same design but in cotton
Does anybody know if they went with the polyester or cotton T shirt or both? Looking at pics I don't see the Mock Turtleneck so I'm guessing they dropped it?