...for those of you without fond memories of the classic Williams EM chime "clank", I may have a solution. 
I rebuilt the chime unit on my recently acquired Argosy on the weekend using old post rubbers and tubing I had around the house (thank-you PinWiki). Having stumbled on this thread I took the opportunity to cover the nylon tops of the chime plungers with a moldable rubber compound I also had lying around called "Sugru". This stuff applies like silly-putty and dries to a hard, durable rubber in 24 hours. I only used about 1/2 a small package to do this.
So now I have rubberized the tips of the plungers and the chimes are a lot less clangy by my ear. Also not as loud in general. I find them very pleasant. 
Sugru (resized).JPG
Remember if you do this that the entire plunger, including the Sugru'd tip, needs to fit smoothly through the coil sleeve so make sure you test it with a spare sleeve before it sets. I also "dropped" the soft tips on the chime bars to flatten them nicely, though I wonder what different a rounder shape at the tip might make? After all, mallets used by percusion instruments are usually rounded at the tips, not flat.
The other good thing about Sugru is you can generally remove it completely with a little effort if you decide later it wasn't a good idea, etc. By carefully cutting, then tearing it away.
