Back in 1935 when the 357 Mag was introduced ,that revolver had a fantastic fine polish and super bluing job. But a job like that requires a very skilled and experienced worker. They are hard to come by today. Thirty years ago if you compared the M27 and M28 they were exactly the same guns except for the finish.The high polish M27 cost 1/3 more than the matte finished M28 !!... Normally the frame inside the cylinder does not show and therefore is not finished like the outside .Don't be concerned ! Enjoy your mountain gun.