Lepper - crazy name, crazy derailleurs - well, actually Taiwanese Shimano copies.

Founded in 1897 in Dieren in the Netherlands, Lepper is one of the great brands of bicycle saddles. Their two fortes were conventional saddles made with high quality leather and those weird two-part stunted saddles that you see on traditional Dutch bikes. Lepper saddles still seem to be available - although, since 2016, the brand may be owned by the all devouring Accell Group and the products may be manufactured in Apeldoorn.

I have not been able to find any decent evidence for this, but I have a vague memory that, sometime in the late 1970s or early 1980s, Lepper decided to extend their brand to cover a wide range of cycle componnets and accessories. They may have done this in association with a Dutch wholesaler. It is possible that the range of Lepper derailleurs date from this time. Some time later they reversed course and reverted to their true selves, as bicycle saddle specialists.

I believe that Lepper derailleurs are usually (always?) manufactured by SunRace in Taiwan.