Solution
G. Husserl Prize, Isreal Ring Tourney, 1966/71
0+9. Colour the pieces. Last move?
Here one of the two Ks is in double check by Rd8 and Qc6. The only possible explanation is that the last move was -1.c7xd8=R+. Thus we conclude that Rd8, Qc6 and Kd6 are White; Kc8 is black. Then further impossible checks are avoided by setting Ne8 and Rf6 White; Pb7 Black. A black Pb7 entails that Ba8 is promoted, so that Ba8 and Pa7 White.
The last move was c7xNd8=R+ because only a Nd8 gives Black something to retract.
