There is a difference in the shuttle between the newer and older, and I believe that while the older can use the new shuttle, the newer can not use the older one - it has a notch in it that the old style does not have.
Bobbins are interchangeable.
Slide plates are, sort of, but may need to be fitted as they were not exact to begin with. The employee would just grab them out of a pile until he got a good fit with that machine, so they may fit tight or loose in another machine. Especially true of older machines. A 27/127 plate is longer than a 28/128 plate.
BTW- a lot of sellers on eBay don't have a clue - I've seen them list items that are totally wrong.