[Retros] a2/c2/f2/h2->N#

[Noam Elkies]

> h2    SPG in 5,5 - Rosler 8/94 (unique SPG in 5,5 moves!?)


Sorry -- since the mate is not required to take place
on the promotion square, there are other ways to do it
in 5.5 moves, for instance this which also works as f2->N:
1 h4(f4) e6 2 h5(f5) Bd6 3 h6(f6) Ne7 4 hg(fg) Rf8 5 g8N a6 6 Nf6#.
Likewise c2->N: 1 c4 e6 2 c5 Ne7 3 c6 Rg8 4 cb c5 5 b:c8=N c4 6 Nd6#,
and a2->N with Black playing a la Rosler: 1 a4 e6 2 a5 Ne7 3 a6 Nc6
4 ab Qe7 5 b:a8=N Nd8 6 N:c7# (all C+ in 10-20 msec. each).

NDE