Raimey, "I" isn`t the same as "J", wether in German nor in English.;-) But it is sometimes difficult to read the old (gothic) letters and so some errors occured.

I presume, the gun was sold by the shop of J.A.Henckels Zwilling Werk, the famous blade and knive maker from Solingen, one of the oldest brands in the world.
Look here: http://en.m.wikipedia.org/wiki/J._A._Henckels

They established a shop in Berlin in 1818 with all their stuff. But of course, it's only an idea, I don`t know if they really dealt with guns…

picture of a showroom: http://up.picr.de/7035286qsj.jpg

Kind Regards,
Gunwolf

http://www.hunting-heritage.com