Is this some kind of glassblowing tool or something else. Thanks

maybe a early electronics soldering iron?

Definitely a soldering copper built for a specific use, what that use was though is anybody's guess.
Probably air/acet buner.

that soldering copper would work good for leaded stained glass work

Joe B

We own a stained glass business (mostly teaching and quite a few repairs now), and I have to say, that would be downright awful for it. Typically you want the handle in line with the tip, gives much better control as the areas you solder are actually quite small. This makes more sense to me for long seams in something, where you could just drag it down them.

Does flame shoot out through the handle to heat the tip? ....I don't understand the method of heating.

Also, I'm far from an expert on glass blowing, but I would say it doesn't relate to that. They typically just use their pipes, ovens, and different bladed tools- no soldering.