I've just seen the video of Seth calling a Double Grand Square:

Looks like the figure was created by Martha Edwards around 2009:

But I found a number of earlier references to "Double Grand Square". Does anyone know whether any other versions of a Double Grand Square exist?

"A double grand square, never before presented for a local audience, is being prepared by B Squares under the direction of Bernice Braddon. Precision timing is the keynote of the square..."

1959
http://www.folkdance.com/LDArchive/1959October.pdf

Exhibitions
Lariat Swingers
Director: Ace Smith
Dance - DOUBLE GRAND SQUARE - American

1978
http://doczz.net/doc/577224/american-square-dance-marcy-1978

"Keith does a fine job on his side, but the dancers felt that a double grand square in the opener, middle break and closer were too many. "

1979
American Square Dance Vol. 34 no. 3 (search for ""double grand square" dance")

"Bob has used a grand parade in his opener, and a double grand square in his closer."
Note: "grand square" is italicized, "double" is not. So it might just mean a Grand Square twice.

2005
http://squaredancehumor.blogspot.com/

"This was one big double square with six side couples and two head couples. The other and even more difficult thing was I could not use my hands. To me square dancing is hands. Every since I started it was right hand this and left hand that. I can’t remember anyone mentioning anything about my feet. Patty was picking everything up just fine while I was slowly starting to get some if it with many gentle pushes and endless pointing by the other Stumblers. And of course there was the caller Ivan patient as ever saying, “George – to the right, the right, the other right . . . very good!” Bill, an experienced dancer, explained carefully how I was to count my steps, especially for the double grand square. Eight steps and turn, repeated eight times, that was the secret for my position."

This one may not be serious! :-)