Zeppelin stamps and covers are extremely popular among "Zepp" collectors and Aviation topicalists, especially in Europe. Those issued by destination-countries which are likely prospects for rapid economic development represent compelling investments.
In addition to their being Zepps, the sets also picture the Russian Icebreaker "Malygin" and a Polar Bear, and therefore have multiple topical appeal to Ship, Animal and Polar topicalists.
The market for better Russian stamps from the Czarist through the Stalin periods is very hot right now. With 142 million people, Russia is the 8th or 9th largest economy in the world, with vast reserves of natural resources and a highly educated population. Since the collapse of the Soviet Union, Russia has experienced several major economic crises in its transition to capitalism, although annual GDP growth has been strong over the last 5 years, at around 7%. The country is still plagued by corruption and organized crime, making it somewhat reminiscent of America during its "Wild West" and Robber-Baron periods. Nevertheless, the middle class has grown from just 8 million people in 2000 to 55 million in 2006.
I favor all better items of Russia, as I believe it likely that both its economy and stamp collecting population will grow substantially over the next decades.
Those interested in becoming part of an international community of stamp collectors, dealers, and investors are welcome to join the "Stampselectors" group and organization page at Facebook. The group and page host lively discussions concerning stamp investment and practical aspects of collecting, and provide a useful venue for those who wish to buy, sell, or trade stamps.