Are those Dummy (attrape) Leitz lenses usable at all? They have glass inside, can they be used - for example wide open only? Or they do not work at all? The same for bodies - to use some parts as spares, like camera bottom, or viewfinder glass?
Optical glass and regular glass are two different things and I suspect even if there's a full lens array included in those dummies, they will give less than sub-par results. If any at all.
There is no explanation that can explain a dedicated collector. I realized this many years ago when I was at a fair and discovered that I had thrown away a fortune in beer cans. Yet, most of the stuff in museums found their sources from collectors.