I think they only kept the water off by virtue of their thickness and density. 😊Apart from the plasticy bit on your shoulders obvs.
They made of wool and quite a lot of it judging by the weight, they were never cheap. Low status, but they are from an era when clothing was a fairly major expenditure for people – all clothing was expensive. Anything made of the same materials these days is going to cost a fair whack compared to heavily marketed polyester and bamboo rayon with a few magic words and an infographic on the swing ticket.
absolute rubbish in rain tho.
Considering how much wool is promoted by the cycling community for its ability to keep the wearer warm when wet, there’s a certain irony in seeing cyclists moaning about a heavy wool jacket being rubbish in rain! Original donkey jackets had thick leather across the shoulders for protection, but vinyl/leatherette was used for mass production, because it’s clearly cheaper.
They’re designed for similar purposes to the Pea Jacket/Coat, although those are somewhat smarter looking it has to be said.
I was seriously considering getting a donkey jacket a year or two back, specifically one with leather shoulder patches, but never went much further than searching online.