Double Square

ThinkFun Binary Arts, 2003.
(plastic, 4-piece square is 3 inches, solved 5-piece square is 3.2 inches square)

People often quickly find the four piece solution and then get stuck trying "stretch" the puzzle just a little bit in a way that will accommodate an additional small square piece. If the four piece solution is 4 units square, it has area 16, the extra square has area 2, and the five piece solution has area 18 (forming a square that is just under 4.25 units square); for each of the pieces in the four piece solution, its orientation is 45 degrees counter-clockwise in the five piece solution:

Characterized on page 102 of the 1942 Filipiak book Filipiak book as "recorded in the records of antiquity", has been periodically made as a promotional item.

CSPI promotional circa 1975.
(plastic, solved 5-piece 2.9 inches square;
this was a company that J. A. Storer's father was a part of in the 1970's;
came with a wire loop which J. A. Storer replaced in 2007 with Snowbird key ring)

Other Versions of Double Square

(5 inches square by 3/4 inch thick plastic box and five plastic pieces;
the square piece was lost and replaced with a green plexi-glass piece)

This puzzle is packaged with a tray for the 4-piece solution and the 5th piece loose; perhaps to guide the solvers thinking away from the 5-piece solution. The directions on a 4.5 inch square card inserted into the back give an interesting discussion of the geometry:

Other Versions of Double Square Continued

Dickinson's Witch Hazel promotional, unknown age.
(3" x 4.5" envelope with cardboard pieces, solved 5-piece square is 4" square;
Dickinson's Witch Hazel was first made in 1866 and was still being made in 2000)

Five Block Puzzle, S.S. Adams Co. circa 1950?
(1/4 inch thick wood pieces, solved 5-piece square is 5 inches square)