Ernst Martin wrote that the Klein-Urania was the successor of Urania Piccola. He said the casing was a sound-absorbing one-piece molding made of Silumin. As well as giving the Urania stability, this made for "the quiet operation of the machine".
Wikipedia tells us that Silumin "is the name used in some countries for alloys based on the Al–Si system. Silumin is a series of lightweight, high-strength aluminium alloys with silicon content within the range of 3 to 50 per cent. Among the advantages of Silumin is its high resistance to corrosion, making it useful in humid environments. The addition of silicon to aluminium also makes it less viscous when liquid, which together with its low cost (both component elements are relatively cheap to extract), makes it a very good casting alloy and a fresher metal. It is also used on three-phase motors to allow speed regulation. Another use is rifle scope mounts and camera mounts."
Now I can say I have a typewriter made of the same alloy that helped power one of Fangio's great cars! I will always remember my father giving me a 16-inch long exact replica of this Mercedes were he returned home from his travels in 1957. Goodness, I wish I'd kept it! The precision manufacturing in this model alone was totally awesome.
Lenin cast in Silumin