The Schwinn Sprint has an incredibly important place in the history of the derailleur. When Schwinn, the leading opinion-former amongst US bicycle makers, rebranded the Huret Allvit with its own precious name it was the definitive sign to the world that derailleurs were ready for the mass market.
Despite its historic role, I always disliked the Huret Allvit. It weighed a ton, its adjustment screws were all over the place and most of all it had too many flat plates joined by too many dodgy pivot bolts. In British weather it either rapidly loosened off and became horribly imprecise or it rusted solid.
One of my ‘derailleurs that changed the world’ - but a mangy dog nonetheless.