Tries in two-mover, "schnittpunkt" theme

In set play, we have 1...Sd6 (a self-block) 2.Sd3 mate (it is OK for White to interfere with the d-line because of Black's self-block on d6. White chooses to close exactly the same line on which Black piece lies like an X-ray).

The pair variation in set play is 1...Sf6, 2. Sg6 mate (White closing the sixth rank, since f6 is a self-block)

The theme of schnittpunkt is the a point where two lines intersect. Let us try 1. Bb1 (or 1.Bc2).Threat is Qe4. This Try crosses the critical square d3. All mates are set except for 1....Sd6! (Now the set mate attempt failes 2. Sd3 dis ch? 2 Kf5!! White is closing his bishop's control of f5 (which is not ok) at the same time he is closing the d file (which is ok).

The pair try is 1.Bh7. Again threat is Qe4. Black this time defends with 1...Sg6! Now white's set mate 2. Sg6 dis ch is not mate, since he is once again closing his bishop's control of f5 (2...Kf5!!), not OK!, whereas closing the sixth rank was ok because of the self-block.

The Key was 1.Kf3! Threat 2.Qh5

1...Sd6 2.Sd3

1...Sf6 2.Sg6

1..R(f,g)8 2.Rxe6

1...Se7 2.Rxe6

1...B(g1->any) 2.Qa1#

In other notes, these two published an Original joint problem in 1955 in "The Hindu", a newspaper which ran a chess problem column that was, after my Rice, Matthews, Lipton, a bit of a Indian weekend entertainment some decades ago. However, 1955 was even earlier than my time....