Pierre DeRoche Chrono Penta PDR 4012 Mode D'emploi page 21

from the letter D (absence of colour) to the letter V (yellow colour). The "Old
Terms" scale is internationally recognised and is the most commonly used. Sto-
nes are classified, by decreasing quality, according to the following terms:
River (Exceptional White), Top Wesselton, Top Crystal, Crystal, Top Cape,
Cape, Light Yellow and Yellow.
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