Wow! Hawg. That is a nice horn. Those don't come cheap if you can find one that really works. Does this fellow do them all the time and dose he sell them? Looks like that would be easyer to deal with than carring a brass flask around.
Shotput it works and is air tight. It has a brass filler plug and a spring loaded valve. He has made a few(three I think) and given them away. He started on this one in Nov. and I just got it a few days ago. I don't want to put his contact info here and have him inundated but I'll PM you and you can ask him yourself.
Hawg Haggen: Nice horn you posted. I'd be proud to carry one like yours. I wish I had the time and patients to do one of these for myself. If your into horns H/H? Check this site for a look/see. rockymountainpowderhorns.com