A white piece which is captured in one phase mates in the other and vice versa.
See also: Cyclic Zilahi.
Jonsson, Bernt Christer
Mat Plus, 2009
2nd Prize
1...Sf3
2.Kd5
Sxe5
3.Kxe5
Sg1
4.Rd5
Sf3#
1...Sc3
2.Rb4
Sxa4
3.Kb5
Se2
4.Kxa4
Sc3#
Pachl, Franz
Schach, 1982
1.Bxf4+
Kg6
2.Bd6
Re3#
1.Rxe6+
Kg5
2.Re3
Bd6#