I’ve always been curious about this, too…
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[some time later, an assemblage of factoids emerges]
http://www.myvitanet.com/fucchiltoot.html
http://www.german-hairbrushes.com/pure_boar_bristles.htm
http://www.taunton.com/finehomebuilding/pages/h00053.asp
And finally, the most fascinating of all…
http://ia.ita.doc.gov/frn/0007frn/00-725-1.txt
Huh. Tariff fights over paintbrushes. Who knew?
Cool stuff.