I Know this is a old post ,
I have been looking into how the bubble lights were made.
Thought others would be interested
The glass was blown into a mold, the liquid is then put in put in the top was heated and crimped and the top sealed.
The diffence in size may be due to wear on the mold.
I believe that noma made all there own tubes ,
I have read that they made some tubes for other companys.
Yes bubble light tubes are still made in fact from what I can find they are made by one company in China.
They had a page on there web site,
on it it showed evey bubble light design that is made today.
I have been researching this to see how it could be done.