I like it. I believe the rail mount is likely original and that this is JVH metal work. The step is due to the bore of the rear sight sleeve being straight or no taper and a section of the barrel turned straight as well leaving it close to flush at the rear with a step as you describe it at the front. The comb seems odd to but I am reluctant to mention a name because while stylistically it would be accurate I don't think you could make the connection. I forget this sometimes, but you could order what you want. If the bore is good I would clean this up and shoot it. I would not blue....that's just me.
