These were a series of cardboard puzzles (see the following pages for examples) that came in a fold-out mail envelope; presumably an inexpensive amusement that could be mailed to a friend or family member. They are based on 1x1 and 1x2 pieces on a 3 x 5 unit board. For example, here is the problem of the "Tank Attack" puzzle (shown on the next page):



The instructions for Tank Attack, like other puzzles in the series, show a filler piece no. 1 for the 2 x 1 empty space, call it a move to remove this piece and replace it at the end, and give a solution of 24 straight-line moves that includes these two moves. However, this solution is referred to as 22 moves. So we won't count those two extra moves her either. Also like other puzzles in the series, the instructions for Tank Attack pose the simpler problem of moving piece 4 to the lower right without regard to where the other pieces end up. Here is a 13 straight-line move solution to do that (or 11 rectilinear moves by combining steps 1 and 2 and combining steps 4 and 5); in the steps below, 0 denotes piece 10:

Electric Corporation Of America, Chicago, Copyright 1942.
(paper envelope and cardboard puzzle, 4.4" x 6.3")

Electric Corporation Of America, Chicago, Copyright 1942.
(paper envelope and cardboard puzzle, 4.4" x 6.3")

Electric Corporation Of America, Chicago, Copyright 1942.
(paper envelope and cardboard puzzle, 4.4" x 6.3")