(from TD 100)  by Henrik Juel 
Around the middle of last century one of the most prominent retro composers was the
Italian Luigi Ceriani (1894  1969). He worked on the heritage from people like Dawson
and Høeg, who both died in 1951, and created the foundation for the modern retro
problem.
Diagram 1 Luigi Ceriani 1. Pr. V. de Barbieri MT 1943

In diagram 1 bQ has just checked, and to enable a previous white move it must have captured. It turns out that we cannot extract a wR and we need to uncapture a wS later, so last move was Qd8xQe8+. The retro play starts  1. .. Qd8:Q, 2. Qf8 Kc2, 3. Qe8 Bf8:S, since a S is the only man who can exit the cage. When it exits, black must uncheck by retracting a bP to g7, and this must be done with bPg6, since the other two would block the 6th row for wK. 4. Sf5 g7, 5. Kg6 Kd3, 6. Kh5 Ke4, 7. Kh4 Ke5. Now wK is out, but wRh8 is caught in the cage, so it must be a wP promoted on g8. wSg8 cannot be promoted as well, since this would require four white pawn captures behind the black pawns, where bRa8 could not have entered.So wSg8 came from f6 while bK stood on d8. Hence we must first retract bQ out: 8. Qh5 Qe8, 9. Qd1 Qf7, 10. Ra1 Qa2, 11. Rb1 Ke6, 12. Kg3 Kf7, 13. Kf2 Ke8, 14. Ke1 Kd8, 15. c2 f7, 16. Sf6 Ke8, 17. Se4 Qa1, 18. Rg8 Rh8, 19. R=h7:S Q=a2, 20. g6:S b3:B. 
Diagram 2

It may be easier to follow the forward play from the intermediate position in diagram 2, where a wS has captured bQ on d8 and bPa7 has captured wRh1 on the bfile. 1. .. bxa2, 2. gxh7 a1Q, 3. hxg8R Rh7, 4. Rh8 Qa2, 5. Sf6+ Kd8, 6. Sg8 f6, 7. c3 Ke8, 8. Kf2 Kf7, 9. Kg3 Ke6, 10. Kh4 Ke5, 11. Ra1 Qf7, 12. Ra2 Qe8, 13. Qh5 Qd8, 14. Qe8 Ke4, 15. Kh5 Kd3, 16. Kg6 Kc2, 17. Kf7 g6+, 18. Sg7 Bxg7, 19. Qf8 Kb1, 20. Qe8 Qxe8+. So bQe8 in diagram 1 is really bPa7 promoted on a1, and its first move after the promotion was Qa2, while the original bQ never moved. Ceriani may have enjoyed the ambiguous stipulation, because he added the Galileo quote "And yet it moves". 
Diagram 3 Luigi Ceriani Source? 1955

Diagram 3 also features an elegant position, for a retro problem, where bQ has just checked; but here it is uncertain whether it captured. I found the problem in a Russian bok without source, although it probably comes from Ceriani's "32 Persons and 1 Author", and I recall that it was a tough nut to crack. It turns out that you need to uncapture no less than six units, before you can begin the proper releasing. Please try to find the essential aspects of the game leading to the position. If you need some more help, it can be divulged that black promoted to S on a1. 