This wine glass has a thick stem and a folded rim. What is its purpose? Is it a flaw or some sale gimmick/promotion?

I am aware of folded foot of wine glasses but folded rim? It weighs 270.9g. Is it 18th century glass or a current one? There are no visible markings anywhere.

Attached some images for some answers!

That has been designed for easy pouring, similar to a jug.
Looks more like a modern design, possibly for kitchen use.

I use that style to mix martinis and strain the ice out when pouring. Usually see them with a glass mixer wiith a bulbous end.