There is a good chance that this is also a reconversion. I don't like the look of the build-up or whatever to the left of the pan.
If it is a reconversion, it's quite likely that the shortening was done by the Confederates. The vast majority of Evans's contract were delivered to the Commonwealth of Virginia as part of their militia act allotments. The brass nosecap has a distinctly military look. I owned a similarly shortened Evans M1816, also with a brass nosecap, that had been percussion altered by William Morgan on contract for Virginia in early 1862.