Thank you Leonf. Aah - so that thing that's closer to the needle that looks like it has threads on it - was that a button and it has perhaps lost a "smooth cap" that screwed on to it? If so I shall try pressing it down and tilting-back. That would be lovely if it is and does - that misaligned slide plate drives me batty every time I look at it. Why oh why would someone try to force it in when it isn't even lying flat in its channel? (The left side of the slide is "down", the right side is "up"! I would dearly love to just be able to lift it up some more and out to that right side but while it is "up" it is firmly "down" on the Japanning of the bed and I don't want to risk damaging the finish.)
Yes - the first time I saw the machines (the Bonita has that arrangement on top as well but you can't see that in any pics I've posted) I thought they must be regal females to be wearing tiaras like that.