The Stravigor evolved from the 5-pointed pen called a rastrum, but instead of fixed points, the Stravigor utilizes rollers. One end of the tool can generate a single stave while the other end is capable of generating two at a time. There is a pad located inside the housing which the rollers brush against for inking. A pair of snug fitting caps prevent the rollers from staining one's pockets.
Igor Stravinsky (1882 - 1971), the famed Russian composer, invented this little dynamo so he could generate staves anywhere, anytime. Using a combination of the first part of his last name (Strav-) and his first name (-igor), he named it the Stravigor. Nikolai von Struve (1876 - 1920), a friend, attempted to patent it for Stravinsky just before WWI in 1911, which never happened.
Most people that find one of these don't know what it is unless they are familiar with stavewriters. Finding an original Stravigor, or accurately marketing one for sale, is very difficult because they have no identifiers. The only markings read "Made in U.S.A." on one side and "Pat. Apld. For" on the other. Neither the inventor's name nor the name of the invention are anywhere on the tool.
Though a patent was never actually awarded for the Stravigor, they were obviously still produced, albeit in small quantities. Igor Stravinsky used his quite often during the rest of his career.