old sidechair without marks in wide-configuration ... zenith?  

Hi Berny,
You don't say whether this shell has the flattened areas or not...
In your first photo, there is at least one dark spot where one of the rear narrow spaced mounts would normally be. Is it possible that a previous owner could have repositioned the original small mounts to fit wide mount base? (As Mark would say "why not?") But if that were the case, there should be some evidence of the mounts having been moved or re glued.
Another possibility (if it is an early shell without flat spots) would be that they may have first tried the wide mount base on a few early shells-- before they decided that the flattened and wider mounting areas were needed. (?)
It is hard to tell from your photos if this shell has the flattened areas. If it has flat spots, it is probably a later than first year shell.
Hope this helps.

hi eameshead
thank you very much!. . .
I have discovered the shell in a junk business under nothing but mud and rubble. Unfortunately, it has been enough only for this pair of to few photos.
But to be able to remind mine me I that there a small elevation was, so not quite flatly.
The Shockmounts are without any mark (no Logo, Letter ... ) and partly defective, so i don't guess that they are repositioned. There are also no rests of glue, I think. The lateral edges are also not curved so strongly, how with a HM-shell. I thought that one can maybe recognise with the help of the patent numbers where and when it was produced?! ..