Just spotted these in a stockbook someone sent me. 5p yellow-olive? I don't remember that. In fact I have no record of it in my lists either. Two phosphor bands. Similar print to the 5p lake shown and colour very similar to the 6p. Have I missed something? Am I going slightly mad?
No obvious signs elsewhere on the strip of discoloration by acid or something, although that has to be my first thought as to what has produced these. A print of the 5p in the 6p colour would be extraordinary.