I have an Alma that is 16 yrs old and in pretty good shape. I got a good deal on it when I bought it recently. I had tried to polish the zipper with brasso and use Apple conditioner on it to make it run smoother. Anyway, tonight I was using a silver polishing cloth to polish a sterling silver ring. My Alma was sitting next to me, I had taken a pic of it for another thread. I decided to use the silver polishing cloth on the zipper and what a difference. Got rid of the tarnish, it's now nice and bright and runs smoother. Here is the before pic.
