I have thought but have no clue about this one !! Will feel utterly stupid when it turns out to be something simple !!
There are an awful lot of us then, mart, as no-one seems to have seen anything like it before.... but it probably will be something 'simple'
I've taken it apart and here is what it looks like ..... even more confusing?
The two end 'blocks' of glass have their ends cut at an angle, for some reason, and the angled 'faces' face downwards?