When doing the first cleaning of a newly arrived case, two small parts turned out to be wedged under a lifted corner of the leatherette of the bottom of the case.
A small (~5mm long) screw-rod and a small spring.
Lucky to have spotted these and glad didn't turn over the case to tap out all the debris and dust. There may be little parts of the machine amongst the debris.
After playing around a bit with the newly arrived typewriter, noticed that the left margin control didn't lock like the right margin. There the location of the found parts, the spring goes over two rods and presses the margin stop release up again into a slot in the margin bar.
Confirmed the importance of carefully checking all nooks and crannies of a case :)