As recommended by Tex Minter of Virginia, who refurbishes Petit and Fritzen handbells:
How to Clean Petit and Fritzen handbells
1.) Remove the handle by unscrewing the nut and bolt. He indicated that he uses a flat headed (slotted) screwdriver and uses a pair of pliers to straddle the bolt. When this is done, lift up the disc.
2.) Remove the two set screws from the yoke and with pliers, untwist the clapper stem. Now push out the axel. The spring will fall out, too.
3.) Put the axel and yoke in the degreaser (kerosene works well) for cleaning.
4.) Make a slurry (mixture) of simichrome, dish washing liquid, and ammonia, wash the whole bell using a sponge with a scruffy pad on the inside and the sponge on the outside.
5.) Rinse with the hottest tap water your hands can stand.
6.) Dry all parts of the bell with a towel.
7.) Use a good quality leather conditioner on the handle.
8.) Reassemble the bell.
9.) Refelt spring and pegs, if needed.