I haven't seen them in person but I would wash them. Dirt is going to ruin fabric a lot more than water. Unless they are falling apart (and they don't look like they are) I would give them a bath.

Hi, thank you for your responses. I've just done a little research on washing vintage quilts, so many ways to wash and so many viewpoints as to if one should or shouldn't. I certainly think after all these years they could use a cleaning. The quilts in this post aren't mine, they are my sisters, so it will be up to them to decide what to do, I'll pass all the info on to them that I can!