Barry Sunshine, a collector of California Fractional Gold coins and a student of the series, has this to say about the BG-501:
BG-501 is a very desirable coin with California Fractional collectors because is it a One Dollar coin with the popular Eagle Reverse. This is the only Period One Octagonal Dollar that doesn’t have a date. This coin is believed to be a Low Rarity 5 with about 65 to 75 known to exist. PCGS alone has graded nearly four dozen, with just a handful of Mint State pieces among them. Finding a Mint State example is possible with some patience and many believe it’s worth the pursuit. If you are putting together a type set of California fractional, then you would probably want to acquire a BG-501 because of the coin’s beauty and its rarity.