The Dutch national team plays in Nike shirts, so they wore the sausage numbers, the 'frikadel' numbers and the DIN-like numbers (see Nike). For the Worldchampionship 2006 Nike designed new shirts, based on designs from 1905 (away) and 1959 (home). The numbers on these retro shirts are inspired by (as Nike says) Dutch architecture, postage stamps and coins. Indeed they remind me of the stamps that Wim Crouwel designed in 1976 (known as 'cijferzegels'). His design was original at that time, but nowadays there are hundreds of fonts based on the same rectangular principle.
PS. Besides the square numbers Nike provided the Dutch team with letters for the player's names. These letters look as if they are copied from a license plate. Some straight angles at the beginning or ending of a stroke are rounded.
The new numbers of the Dutch team are inspired by Dutch coins, Dutch stamps and Dutch architecture, but they can also be reconstructed with Dutch toiletpaper.