The plastic timer dial broke.

A 30 second repair; I simply slid the new part over the D-shaped metal bar that projects from the dryer, then snapped on the old dial knob onto the new dial skirt.
Initially, I bought the part from a national realtor's internet part replacement site. I carefully described the part as having a "central cylinder about 1 1/8 inches in diameter extending out about 3/4 inch from the flange." received the correct part from Part Select.