Bubble seperator Mk1

 

That looks to be a charcoal Canister part of the Emissions System.



That is probably made of unobtanium as it is an Ancient part.

There are how to's on rebuilding them, the one I usually link to is devoid of pictures…

I needed one some years ago.
Could not find a new one.
If it is clogged you can try to clean with carburetor cleaner.
Otherwise buy a metal MkII, but than you loose originality.
Kris