1.Sa6 threat 2.Qxa5+ Sxa5 3.Rb4
1...Kxb5 2.Qd7+ Kc4 3.Qa4; 2...K else 3.Qb7
1...Bxb5 2.Qh4 S any 3.Bc2; 2...B any 3.Bc6
An attractive lightweight, with the queen switching from one side to the other. The problem has a second, unforced threat, 2.Bxd3, which could be eliminated by, for example, starting the black bishop at e2. This was the era when model mates dominated the three-mover, and Behting wished to include the model 1...Bxe4 2.Qxa5+ Sxa5 3.Rb4. There is a second model when the king reaches a6, and a third (with essential double check) in the line 1...Bxb5 2.Qh4 Bxa6 3.Bc6. 1.Bxd3? almost solves, with the white king revealing its function as a cookstopper after 1...Sd4!
Satanick Mukhuty: Surprising key! Not trivial at all.
The next problem posted here will likely be on Monday July 14th, as I am travelling for the WCCC.