Re the article on ribbed steel liners on rotor
housings. Several times on rotor housing for sale on
Ebay mentioned "slight flaking of chrome on the
edges". What does that mean?

(Some guy that never signs his letters.) Hurant

That means the corner seal took a chunk out of the edge of the
rotor housing. Some after market apex seals are not split
right at the corner and are split about 1/4 along their length.