A small round or egg shaped piece of glass, crystal or stone such as marble or agate used from the 18th to late 19th centuries to keep the hands cool. Most were about one and a half to two inches across. Some were eventually made into miniature paperweights and others intricately carved by glass houses such as bacarrat and clichy.
Found on http://www.antique-marks.com/antique-terms-h.html
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