That's a wonderful piece. I was unaware that Greener's went back into the percussion era. Any idea as to the date of manufacture?
Your photo reminds me of something I've been meaning to comment on. Many photos of original pistols and shotguns from the 19th century indicate that loading from a flask was a common practice. Yet, rifle shooters of today often advise to avoid this as the flask or horn may become a bomb from residual bore embers. While this seems to make sense, I have never found a reference relating to an actual event. Perhaps this perception is related to the well intentioned guidance offered in the Black Powder Bible publications from the 1970's.