OurWorkbench

If you have a 1935 manual for a 66 machine it shows side clamp feet. Your machine looks to have what are called back clamp feet. The back clamp feet are like the ones seen at http://needlebar.org/nbwiki/images/1...tachments2.jpg There are some other images for attachments for the 66-1 machine at http://needlebar.org/nbwiki/index.ph...ts/Accessories

I think you are referring to the slide plate that goes over the bobbin. A lot of time they do go missing as they are kind of fiddly to replace correctly. How to replace it is shown in the manual as seen in the lower right corner of this page of the manual
https://www.manualslib.com/manual/12...?page=6#manual There are replacement ones available one of which can be found at https://www.amazon.com/KUNPENG-1PCS-...CV5/ref=sr_1_1

As I noted in my previous post, this machine will use class 66 bobbins. I have heard that some have had troubles with new bobbins not working correctly on these very old machines. I have lots of old bobbins, so haven't had to purchase any new ones.

I don't know what condition the belt is that is wrapped around the arm of the machine. If you are taking it off and it falls apart, a new one would be needed. If it comes off in one piece and is fairly supple you may want to try some leather conditioner. I looked up a few links about doing that or using something else.
https://www.quiltingroomwithmel.com/...ose-belts.html
https://www.practicalmachinist.com/f...-belts.293241/
https://sewingwithnick.wordpress.com...t-maintenance/

Looking forward to see some more of the machines that you have come across.

Janey - Neat people never make the exciting discoveries I do.
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