(a) The White has got only a Bishop and a Knight.
(b) The white pieces, B and S, will form with pericritical moves a battery which will fire with double check.
(c) The black in two variations makes different castling and is mated in the eighth row.
(d) No replacements of pieces (for twinning) is allowed.
Source: WinChloe, no. 487666
r3k2r/8/8/4b3/8/4S1q1/8/1K1B4 (3 + 5)h#3, 2 solutions
1.0-0 Sd5 2.Bh8 Bb3 3.Qg7 Sf6#
1.0-0-0 Sf5 2.Bb8 Bg4 3.Qc7 Sd6#
Here is shown the idea in simple form. The wB could be positioned on e2.
The wK, to avoid checks by bR and bQ, could be only on columns b and e. But, with wKb5 the solutions are 1507, with wKe6 the solutions are 1283 and with wKe4 the solutions are 32. The wK is very well placed on b1!
The white movements are not pericritical, they simply form the battery.
If we force the restriction h#3,5, then many unwanted solutions appear, 68 in total.
JT Feoktistov-50, Shakhmatnaya Kompozitsiya 1998-2000, 1st Honourable Mention
Source: WinChloe, no. 161976
r3k2r/s7/1p2B3/p2S2q1/4p3/3b4/8/b2K4 (3 + 10)h#3.5, 2 solutions
1…Bg8 2.0-0-0 Bh7 3.Kb7 Bxe4 4.Ka6 Sc7#
1…Bc8 2.0-0 Ba6 3.Bh8 Bc4 4.Qg7 Sf6#
The nice movements of the wB are pericritical and the bishop forms the battery in both variations. But the two mates do not happen on the eighth row.
Ioannis Kalkavouras and Emmanuel Manolas
h#3.5, 2 solutions
1…Bh3 2.0-0 Bf1 3.Bh8 Bc4 4.Qg7 Sf6#
1…Ke2 2.0-0-0 Se3 3.Bb8 Sxf5 4.Qc7 Sd6#
In one variation the white battery is formed by the wB moving clockwise, and in the other by the wS moving anti-clockwise.
The two mates appear symmetrical in the eighth row (vertical mirror, echo mates(0,4)).