Which books are you comparing, Keith? Someone might be able to give you an idea of how far you can trust various attributions from different books.
There are all sorts of errors which can be made. The worst are where the authors have pulled an attribution from nowhere, but state it as fact. Better are those where the author at least acknowledge the guess. Best practice, however, is to either only give a definite attribution when there is definitive proof (design books, design registrations, etc), and if a guess has to be made, then probabilities and evidence should be stated.
Even so, it's possible to be wrong, especially as if a company's designer noticed a particular design was popular, they wouldn't bat an eyelid at copying it. Thus you might get such extremely similar designs from different factories that you can't even distinguish them from the catalogues. This was prevalent in the 1930s so maybe it's reasonable to assume it would have been happening earlier as well? (Do people agree?)