[Retros] Accidental retro

[Noam Elkies]

Leafing through a copy of Laszlo Polgar's _5334 Problems, Combinations,
and Games_ that I saw on a coffeetable earlier today, I noticed
the following miniature in the Mates In Two section (#2940, p.547):

  W Kg6 Rf6 Nc8 Pe6 Pf7 = 5
  B Kf8 Pe7 = 2

  +-----------------+
  | . _ N _ . k . _ |
  | _ . _ . p P _ . |
  | . _ . _ P R K _ |
  | _ . _ . _ . _ . |
  | . _ . _ . _ . _ |
  | _ . _ . _ . _ . |
  | . _ . _ . _ . _ |
  | _ . _ . _ . _ . |
  |_________________|

The retroanalytic content is surely not intentional:
The entire chapter is marked "Mate in Two, White to move",
and all the problems in this section are miniatures where
White has a set mate to each Black move but, for lack of
a neutral waiting move, must find a key that either changes
or adds to the set mate(s).

NDE