Sorry Carla - I couldn't find a date on the article either . . . I was just going off the date that Jason posted on the site
http://www.classicseacraft.com/broch...cle/index.html
When you view the link and you double click on the article the page it gets bigger.
I dug up the patent online and posted it below for anyone who is interested. Looks like a neat design with 2 compartments on each side . . . looks like it holds a LOT of water.
3503358 Patent