Rust stain dilema.

I have a set of collector plates that were given to me when my children were little. I haven't had them up for years, but would like to put them up in the room my granddaughters use when they stay here, so pulled them out the other day. The metal plate holders were stored with them and one has left a small rust stain on the surface of one of the plates. I was afraid of using a comercial rust remover for fear it would also remove the paint on the plate. Does anyone know of a gentle way to remove rust? It's really pretty small, so I'd rather leave it than ruin the picture underneath it, if I have no other choice.

Kathy