For those interested - here are some photos of the Flap Type Mae West.
Following up to a previous thread - note the Kapok Pillow contained in a pocket on the reverse of the cape flap. This pillow added extra buoyancy for the flap.
Some people speculate the pocket was for hand paddles. It can be seen by the photo, the pocket was for a standard front lobe kapok pillow.
I have other photos of this vest if anyone is interested.