This may be the most beautiful matchbook of its time. Wikipedia:

Soon after their renaming to the Detroit Fuse and Manufacturing, the company adopted their famous logo: a capital letter D for Detroit enclosed in a square. The logo was stamped on all Square D's switches and products. The combination of an easily remembered monogram logo and their great popularity resulted in customers referring their products as "Square D". Consequently the company trademarked the logo and in 1917 they renamed the company to Square D.

Bought by another company in 1991, but still around.