This post is about the 15-91 that came from a smoker's house. The beast is mostly finished. Almost all of the gunk and grime is gone from the outside and still have some inside to clean but I ran out of cottonballs. 2 bags gone through for this project. I will recommend to smoking SIL that she clean her machine yearly at least to remove the tar buildup. She probably won't but I'll have said it at least. Had to pull head out of cabinet to take head to sewing shop to find right size screw for tension disks for bobbin winding. Found out that there are 2 little screws to remove so you leave hinges intact and just pull machine from the hinges. Yeah!!! Ladies at local sewing shop were fabulous with helping me find the right screw and also picked up some vinatge 15, 66 and Bernina bobbins while there. The screw was not vintage but it worked and I was just happy to have found one that fit. Almost scored a vintage bobbin case but it was missing a piece. Thanks to all who gave me ideas as to cleaning the nickel pieces on her.