I have noticed that on so many of the better Tiffany pieces from the 1880 period that have come up on the market a large percentage bear French touch marks. They were obviously sold in France and most probably at the Tiffany store in Paris.
I am aware that the Tiffany Paris store was very important in the last quarter of the 19th century. In fact I was told by a reliable source that the Tiffany store in Paris was treated on a par with the New York store by Tiffany and Co.
Chatting to a very knowledgeable collector who was showing me a museum piece of Tiffany from the 1880s the other day, I drew his attention to the French control mark. He shrugged and calmly said that France was where all the money was at that time and where the real collectors were.
Putting it all together, I would guess that many of the important pieces were sold in France and that was mainly because the economy was not so strong in America at the time. Most people do not know that Wall street went through a terrible period in the last quarter of the 19th century.