Atco Standard Villiers carburettor

Does nobody have any ideas?

You'll need to show more pictures to identify the carb, all you've shown is the base of the float chamber which was common to more than one Villiers carb.

And maybe some dimensions e.g. outside diameter of the stub which it fits. 

What's different about the needle system, and compared to what?

What mower is it from?

I uploaded a section from an old Villiers booklet which covers the carburettor. It may contain some of the information you're looking for:

https://oldlawnmowerclub.co.uk/sites/default/files/opmanual/Villiers%20Carburetter.pdf

Thanks for the website address it is exactly what I was looking for. I scoured the internet with no luck at all. Once again thanks 👍👍