Janey - You are neat people. Very neat people! Thank you so much for all that info. I'll be sure if I want to post an image right in a thread from now on to make sure it is under 2MB.
The second document is the instructions on how to use a needle-threader. I think it was a Singer one but I'm not sure. The three machines in Sewing Room are that Belvidere, a Bonita and a Unity (that's the hand-crank). I was so excited when I first saw that green "manual" but on looking inside saw it was a catalogue of all the various cabinet styles etc you could get.
I can't remember if it had other Belvidere machine models in it as well but certainly it had no instructions at all. Luckily there are some 20x1 needles in the Sewing Room (quite a few of them) and, happily, that's what I put in the machine when I wanted to thread her up.
All the info you've provided is wonderful - thank you. Having a look at the treadle table it's in, do you know how I'd get the machine out? Are there, for example, likely to be grub screws like there are on the Singer, or is there something special about it? That threaded metal screw/bolt end sticking up from the front of the bed at the sewing end looks so wrong to me. It would catch on your work when you sew.
I agree about 3-in-1 too, if I want to loosen things up I use deodorized kerosene and if I want something to penetrate I use Kroil. (I'd love to try Blue Creeper but can't find it in New Zealand or any overseas seller who will ship it here. <<sigh>> I've heard it's a miracle worker) Aside from I only use pure, high quality sewing machine oil. (Except on gears that need grease, and I'm just as fussy about that. I can't Tri-Flow here - so I use grease from The Featherweight Shop. :-)
Well - that's enough of my burble. Now that I know just what machine it is I'll see if I can find anything useful online in terms of manuals or instructions. It makes a huge difference just properly knowing what to search for.