The switch of the Machine Robot usually has the same colour like the small gears. Gernots last picture shows an exception - small red gears but a green switch. Never ever saw a Machine Robot with a non-translucent switch. Let´s take a look to production dates. The Machine Robot was produced in 1963. Following an iron rule of toy industries - every year a new toy - in 1964 came out the Engine Robot. 1965 appears the Fighting Robot, another robot with that switch. First examples also had the translucent switch. Later (in 1967 for sure, perhaps even earlier in 1966) the switch turned into the well known red non-translucent version. Therefore we can date the change of the translucence to 1966 or 1967. Means the 1963 Machine Robot with non translucent switch isn´t right. Just my two cents.
Remember dutch band Golden Earring and their big success Radar Love? Golden Earring - Radar Love They hade their next big hit in 1973 with Instant Poetry. Be sure to see some Horikawa Robots! Golden Earring - Instant Poetry
PW is Progresswerk Nürnberg. The company was founded in 1863 and was in business until 1993. They made fine leather goods. From 1953 to ´73 also plastic toys were produced. More information ( german website) on: http://www.avkits.net/kit70/p/progress2/einleitung.html
Some Progresswerk plastic trucks with same flying saucer as space gun has