So, progress report.

I've cleaned and oiled; dis-assembling the tension unit (which is weird) and the shuttle race but nothing else. It's not in bad condition and I didn't need to take anything else apart to release stuck mechanisms or whatever. As it's more complicated that a hand-crank Singer, and I have no manual I decided discretion was the better part of valor. If it moved easily, I left it intact 

I've threaded it, and test stitched a straight line, and... it sews!
Tension seems sweet even though I've had it apart, stitch length does vary as it should, although the numbers on the dial had me confused. They go from 6 through 8, 13, 25, right on to 55. But 6 is the longest?
We think the numbers must be stitch per inch or similar, because it's definitely 55 is the tiniest, and 6 the longest.
The settings were full pressure on the foot pressure, full height on the feed dogs, and 'M' on the B.A.M. slider.

Now I'll change feet on it and start with zig-zag and see how it goes, but I was excited to share, and this info might prove a useful resource eventually to someone else with a machine like this.

P.S. It might be a male, this machine. And I might call him Valor. What do you think? It's certainly the heaviest machine I own.

Thanks for the info and support Arrow 
You're right of course, I need to get it cleaned and running and then I guess the mechanism will become self explanatory! It's just that I've never seen one quite like this, and any input from anyone who had similar is appreciated.

It might be Buttonhole, Automatic, Manual. It does have an integral cam, and if you give it some width and set it to B I think it's doing a set of stitches that could create a buttonhole edge. Although whether it's reversing or you have to do that bit yourself yet I'm not sure.
I have a copy of the manual for a Pinnock Trendsetter, and that had some fancy buttonhole potential, with a dial and lever and so on, so perhaps this is a different way of creating the same effect. Time will tell.

A nice fun adventure for the new house 

Thank to everyone. I'll keep you posted.   

Yes looks pretty much the same doesn't it?
Mine has a round hatch in the top (which that one may or may not have) for "embroidery plates" or what we would now call 'cams'
But I don't yet know which cams would fit it - Helen Howes' first shot at it don't fit, so it may be a long process


But it's a lovely looking thing, and the electrics appear sound, so I am going to keep working away at understanding her and getting her running. (I think she's a she, but no name yet LOL)

Okay, I have a Japanese made machine, branded as a Pinnock but the same machine also appeared as a  Sewmor and possibly others.
There are several things I haven't figured out about it, but here's the first one.

Where you might expect the L(eft) C(entre) R(ight) needle position slider, I've got B, A and M. I can see that they do something under the bonnet, but I can't figure out what. It's connected in some way with the cams which fit into same area, but as I don't have any cams I can't determine what effects might be.

Does anyone have any knowledge of this type of machine please?

Thanks
Leila

Quite true 

It looks to be in fair condition for it's age - without being able to see underneath - but if it's going to be your first vintage Singer be aware that it doesn't appear to have any tools, bobbins or feet - not even a standard presser foot if you look closely.
So the price would have to reflect that you're going to have to find some spares before you can use it for even the most basic stitching.

Still a pretty thing, and the 99K is a small neat machine 

This machine has now been disposed of - thank you

Interesting!
I knit so slowly I don't have to sew up much anyway LOL but that is a great thought. Thank you.
Leila

Hello and thank you! So glad to have something like "the old place" back up, and no doubt this will prove to be even better with time. Nothing happening in terms of sewing or machine maintenance here right now, moved just 3 weeks ago and all that kind of ting still in boxes, but it will come...

Best wishes to all
Leila