@Bwassa. I think, I can help you. The first english guide was published in 1964, it has the same cover as the german edition. Until 1992, the english versions had always the same cover like the german versions, with one exception. In 1988, for the english version was used the german guidebook cover from 1983, so the 1988 german guide has another cover.
In 1992, the first international guide was published with a serval on the cover. The german guide of that year has night monkeys on the cover. In 2000, the second intern. editon was published ( young gorilla)The german version has polar bears on the cover.
In 2007, the third english edition has Knut as cover, the german version has hippos on the cover. The latest english edition was published in 2009 and has the same cover as the german guide, an Aye-Aye.
If you have more questions, please feel free to ask me.