This USSR patent is closely related to German Patent # 1,605,804.
It was filed, in 1966, by Georgy Panin of TSKTB (ЦКТБB or ‘Central Design Office for Bicycle Construction’) in Kharkov, Ukraine. It is for a very clean derailleur design with two sprung pivots and a short, racy, pulley cage with an offset pivot point. A particular feature is that the low and high gear stops are adjusted using thumbwheels. All very reminiscent of the 1961 Simplex Juy Export 61 and some features of the 1964 Favorit PWB.