What a fine piece of detective work! I would be interested to know whether the Mendes I. Cohen collection included any small California gold (not mentioned in Adams), and if so, whether any was purchased by "Roberts," but I don't have an email address for Dave Stone. I'd like to know the lot numbers (and descriptions, if possible).

I spent a couple of days in the American Numismatic Society library around 2001-2002 when I was researching the 2nd ed. of California Pioneer Fractional Gold, tracing early sales of these pieces in named catalogs, but did not get around to the Cohen sale.

The Arms of California half dollar is slightly controversial because its dies are not shared with any other issue, and its first known appearance is 1877. While this puts it squarely within the correct time period, which extends to 1883, Mike Locke suspected that it may be dated earlier than its issue, and I wondered whether it might not be a fantasy gotten up to sell to the wealthy Fonrobert. I am still anxiously looking for an earlier appearance than 1877.