World's most valuable picture postcard?

Shown above is probably the most valuable picture postcard in existence. The sender, a Russian immigrant, used a 1959 5c St. Lawrence Seaway invert to mail the card to London, England. The message reads in part (in Russian) "plans have shattered - in the heart and in living conditions..." Part of the Peter Balner Collection, it sold for $12,000 in 2002.