This Trader's image suggests that this copper kettle is 18th century. I have yet to see an 18th century kettle of this size. If one existed, and documentation exists, then I would genuinly appreciate someone showing it to me.
Powder horns it must be said are like a bomb hanging off your shoulder. I know this sounds frightening, and the last thing I want to do is put people off the sport or stop living historians from carrying their powder horns, but the danger exists.
There are several ways in which a powder horn can explode. One is if you leave the stopper out after loading and a spark gets into the horn from you firing your gun. Another is wearing the powder horn when lighting the camp fire. The stopper in the end of the horn can build up a black powder residue around the stopper, and a spark landing on this can result in an explosion.
For these reasons, the base plug is NEVER glued to secure it. It is only sealed with beeswax and secured with no more than 6-8 small pins or wooden pegs the size of a toothpick. The reason for this is so that IF the horn should explode, the pressure will blow the base plug out of the horn instead of fracturing the horn.
Seeing as this manufacturer has seeminly no knowledge of the danger he is creating for his clients with this horn, I would strongly question the safety of the other horns that he makes.
If you are going to purchase a powder horn, ask the seller how it has been constructed. If he/she can't tell you with any certainty, go somewhere else. Place your life in your own hands, not in the hands of the trader or the manufacturer.
The other problem with bought horns, is that some makers do not seal the plug with beeswax, and powder residue can leak around the base plug. The danger here is obvious. Blow into the horn and see if it is sealed.