A solid gold Poljot caliber 2200 wristwatch produced by the First Moscow Watch factory circa 1965. At 1.85 mm, this is the thinnest Soviet mechanical movement ever produced and one of the thinnest mechanical movements ever produced anywhere in the world.  Fewer than 6 pieces of this caliber are known to exist. This caliber was never put into production because the bridges were so thin that they easily deformed in everyday wear. The few that were produced were put in solid gold (.583/14K) cases w/Soviet hallmarks.