OK, here's the bottom line on this overshirt joint: it's sick, there's nothing like it, and you should strongly consider adding it to your rotation.
This style, from Wax London's continuing Whiting collection, comes in a heavyweight cotton weave fabric. This unique cloth was sourced in Portugal from an archive dating back to the 1950s, making it rather unique.
It features two patch pockets and Corozo Nut buttons. It's best worn as a relaxed-fit shirt-jacket with a T-Shirt!
There you go. You're welcome. It's your new look. Thank me later. --Justin