Good day. I am doing a bit of research on friends newly acquired revolver and have a question about a marking . First off the revolver is an all original (un-modified) .455 2nd model . It is in very nice condition and appears to have seen little use. The piece has all of the standard markings with the exception of what looks like an X with a line through it on the left side in 2 places . Any and all comments are appreciated. Many thanks in advance. Markings are in second pic.