The top of the Marlin 1895 rifles should be sandblasted. At least all of the dozens I've seen are sandblasted.
Try using a scrap of fine emery cloth (200-400 grit) and tap with a small hammer. The grit particles simulate the sandblasted finish, and you can roughen up the scratch until it blends in with the meta. Degrease using alcohol or acetone, and apply cold blue to darken the scratched area. Oil and you are done!
HTH
John