Gas Balloons (Not Hot Air Balloons) On Stamps

As a (now retired) chemistry teacher, both hot air and gas balloons have been a great source of material.
There is already a topic Show Us Hot Air Balloons!, but some of the postings have shown gas balloons, almost always using hydrogen.
I suggest we don't include party balloons!

Here is a first contribution to the topic, the USA aerogramme issued in 1995 celebrating Thaddeus Lowe :

This is the photograph which was the basis for the design:

wtcrowe posted a fascinating scan of an envelope addressed to Thaddeus Lowe

WW2 Barrage balloons:
UK (Jersey) 2016 Battle of Britain commemoration:

Turks & Caicos 2000