Sadly in this era of mergers and acquisitions one finds information on vintage appliances/products is just not available. Much of it is chucked away as rubbish as things are consolidated/sold off, or simply "lost" in the process of several M&As. Also many of the old timers are either retired, dead, or otherwise not around to give any assistance either. Now and then one lucks out and finds such a wonderful person, but alas, unless they have their own stash of information, much is also gone.
One company I found has an excellent "vintage" appliance information department was Wearever. Needed information/manuals for my vintage bake oven, and not only did they know what one was talking about, but sent the original manual/recipie book.
L.