Could be referring almost anything. If it were mine I'd want it to be something like C company 25th West Virginia (have no idea if such a unit even existed though).
Can't find anything on a 25th West Virginia but there was a 25th Virginia Infantry & Cavalry regiments. I'd question those markings as to why the C looks a different type cast than the W V and the 25 does not match either plus is out of place.