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Please explain how shell dealers grade shells

Shell dealers and their shell-buying customers worldwide use the HMS-ISGS Shell Grading Standards. These standards, first published in the Hawaiian Shell News in September 1977, are as follows:

Gem:
A perfect specimen with an unblemished spire, unbroken spines and lip without chips, fully adult and normally colored -- a shell without a visible flaw. Well cleaned inside and out, with original natural gloss and color. Bivalves must have both valves, matched and unbroken.

Fine:
An adult shell with only minor flaws and with not more than one shallow growth mark. Must have original color and gloss. A cone lip may have one small chip, a murex two minor frond breaks. No repairs, such as filed lips, mended knobs or filled worm holes.

Good:
A reasonably acceptable shell with a few defects such as growth marks, broken spines, worn spire or lip chips. Specimen may be subadult, but still must faithfully display all the characteristics of the species.

Commercial:
May be obviously dead or beach collected, with chipped lips, faded color, growth faults or imperfect spires. Shells of Commercial grade are not acceptable for mail order retailing and should not be offered as collectors' specimens.
Grades may be abbreviated as G, F, Gd. & C.

Supplementary symbols:

  • W/O = with operculum.
  • F/D = full data (area of origin, habitat, date and original collector).
  • B/D = basic data (less than full data).
  • + (plus) or - (minus) may be used with quality label (i.e., G- or F+) in borderline cases.
  • JUV = juvenile, for Good and Fine only, in lists, tags and letters.

These standards are constantly being questioned and tested as users encounter new needs. For instance, the scientific value of shells depends on the locality data more than the condition of the specimen. Minor breaks and flaws often allow one to infer something about the animal's lifestyle and its predators. Many believe that the grading of locality data (F/D, B/D) should now be divorced from the grading of the quality of the specimen.

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