For some reason that name sounds familiar.
However, search after search didn't reveal anything more than what you already knew.
"Kohl, Conrad—Built a gunshop in Reading, Berks County, Pa., in 1851. Active 1859 and after".
I also found another interesting bit of information.
It has been recognized for a very long time that many "Gunsmiths" of the time did not build the complete rifle, very often specializing in parts, or assembled parts.
The following led me to thinking that C.Kohl could have been a Barrel Maker.
"At a power source further above on the stream, Kohl and Keim had another gun barrel factory, which then became a saw and clover mill for Joseph Schoener and then Amos Price. Near the head of the stream Moses Ruffner had a stave mill and John Gougler had a small woolen factory around 1862. After the manufacture of gun barrels declined, many of these sources converted to hat making".
The part about "had another gun barrel factory" leads one to wonder just what the original "gunshop" was building?
All very interesting, but not much help to you.....
Uncle Russ...