One small difference: in the boxes, the notches are filled with #19 stones. With those stones in place, the NS arch substitutes nicely for an NF arch; without them the NS arch provides some additional interesting options.
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Good block play.
Construction with toy building blocks and such, for fun or therapy
Ankerstein, Unit Blocks, fischertechnik, Kapla, Froebel, Lincoln Logs, et al
Copyright Alan Winston, Seattle -- all rights reserved