The gold finish was applied by electroplating the object with 24K gold. This is really a misnomer as dor comes from the latin for gold. This finish has the acid speckling of gold dor , but is darker. The rarest finish on Tiffany objects is silver. Most probably it was special order.
Some patterns come in more than one finish.
For example, Zodiac desk pieces come in patina, gold dor , statuary bronze dor , and rarely in silver. Other patterns are found in only one finish. Bookmark, Ninth Century, Abalone, and Venetian are examples of one finish patterns. Variations can still be found. Occasionally hand enameling was added to some patterns such as Zodiac or Bookmark.