The technical Hoepli dictionary says: crescent (circular notch in the periphery of the roller of the lever escapement. But this is in the field of orologeria (watchmaking, horology). Not exactly what you are looking for. But found nothing else.

Crescent Moon - Symbol of Islam?- [ Traduci questa pagina ]The Christians have the cross, the Jews have the star of David, and the Muslims have the crescent moon, right? What is the history behind the crescent moon ...
islam.about.com/od/history/a/crescent_moon.htm - 24k - Copia cache - Pagine simili - Salva risultato

Symbols of Islam - Wikipedia, the free encyclopedia- [ Traduci questa pagina ]The star and crescent is commonly regarded as a symbol of Islam. It is featured prominently on the flags of many countries in the Islamic world, ...
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http://en.wikipedia.org/wiki/Crescent


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Note added at 16 min (2008-02-27 10:44:34 GMT)
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In art and symbolism, a crescent is generally the shape produced when a circular disk has a segment of another circle removed from its edge, so that what remains is a shape enclosed by two circular arcs of different diameters which intersect at two points (usually in such a manner that the enclosed shape does not include the center of the original circle).



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Note added at 18 min (2008-02-27 10:45:57 GMT)
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Mezzaluna (Islam)
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Una tipica mezzaluna e stella che campeggia su molte bandiere di stati islamiciLa Luna crescente con una stella è il simbolo da un certo momento storico in poi internazionalmente riconosciuto per la fede islamica. Il simbolo è presente su alcune bandiere di Stati musulmani (Azerbaygian, Turchia, Maldive, Pakistan, Turkmenistan, Uzbekistan, Algeria, Mauritania, Tunisia, Comore).



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Note added at 5 ore (2008-02-27 15:52:53 GMT) Post-grading
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http://www.theskinnercompany.com/ps_economy_clamp.htm

Wide: 8" wide for running corrosion spots, complete with a crescent shaped, pressure equalizing gasket of Skinner Special Composition for use on oil or gas lines.

Use a Wide Clamp with a larger, crescent-shaped gasket to seal corrosion spots



http://edu.cqdx.gov.cn/car/30313.html

I had my up pipe for our local meet which means its been on over 800 miles now. This makes me think it's not the crescent gasket thing. Could be a turbo oil line too.