I that is written in his hand, he may have intended to do it, just not sure how he wanted to execute it.
An interesting piece of art that! Personally, I'd leave it as the artist intended. As for the bayonet itself, it is, or was, a Prussian 1809 pattern 'Potsdam' bayonet. These were generally in use from 1809 to 1839, when the new pattern was introduced. These bayonets were still in use and being imported into the US during the Civil War. So far as I am aware, there is no record of the Confederacy buying weapons from Prussia, though they may possibly have captured some quantities of them.