From: Alain Jeanroy
Email: alain.jeanroy@laposte.net
Perhaps it is a "Pied du Roy"; an old instrument to calculate angles. Was also useful for division in equal parts, to trace polygons, the measurement of arcs and cords. You can see pictures at http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&category=23881&item=6156431981&rd=1#ebayphotohosting
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