These items I'm pretty sure I have a idea what they are.
Hi Pekka,
Nice machine! I have a AI Hembrug universal grinder that looks a lot like this one. If I recall right, it was "copied" from the Cincinnati as part of the post-worldwar 2 help to restart the European economy. It is not a carbon-copy, but similar enough to see the relation. I recognize a lot of the attachments, amongst which the one on photo 3 top centre. But I don't know what it is for (it is not in the manual). Can you enlighten me? I also recognize (i think) one of your unknown parts in the next message. (second photo, top right, with the angle-scale on it) it should be most of a clearance angle setting dog (to grind clearance angles on milling cutters for example). The missing part looks (at least on mine) like a "horse shoe" with a pin attached in the middle. Maybe that part is lurking somewhere under other stuff? If not I can provide the measurements of my part. It should be quite easy to make.

I have instructions on it's use in Dutch somewhere, if you are interested I can translate them to English for you.
If you are interested I could also email you a digital manual of my machine, perhaps it could be of any use to you because of the similarities? It is in Dutch AND English, so you should be able to read it

Peter