Does the muffler knob, just turn or is there a slot in which it trips back and forth like a toggle switch? The frame of it resembles very closely the Trowa muffler. The earlier Trowa, that I have is from about 1950, I think. It has a wooden pad base like the Deri,which is screwed into the muffler frame; it is therefore tight but the later version from about 1965 has a steel pad base which is riveted and it is wobbly, until engaged with the head. It doesn't seem to matter. It doesn't rattle ,when disengaged and works flawlessly when engaged.
The toms do have a dark colour but it is much redder than Walnut. It is highly unlikely, that the Germans would be using walnut anyway, because the dark, lumber walnut is from the Black Walnut of N.A. and has always been very expensive, due to rarity. The Carpathian or English walnut of food commerce is an entirely different wood. Take a very close look at this material. The shells are very thin,dark,reddy brown, without rerings, the same as the older Bongos, I have that I am sure are Deri,which are made of a hard pressed composite.. I suspect ,that yours, are unusually heavy as well. Look at the edge with a lens and see if there is any endgrain. I bet they are a composite.