The Momsen lung, a primitive WWII rebreather for escaping submarines.
Fullsize image: https://s3-us-west-1.amazonaws.com/h...g_fullsize.jpg
https://s3-us-west-1.amazonaws.com/h...omsen_lung.jpg
Previously:
https://www.homemadetools.net/forum/...539#post162559
https://www.homemadetools.net/forum/...934#post137540
https://www.homemadetools.net/forum/...4385#post79850
https://www.homemadetools.net/forum/...984#post160478
https://www.homemadetools.net/forum/...2209#post75951
https://www.homemadetools.net/forum/...562#post166750
https://www.homemadetools.net/forum/...862#post167681