[FEN "8/8/8/6pp/6pk/R7/6KP/8 w - - 0 1"] 1. Rh3+ gxh3+ 2. Kf3 g4+ 3. Kf4 g3 4. hxg3# 1-0
What is the source of this simple chess problem (White to mate in four) which somebody showed me at a chess club 50 or 60 years ago?
I suspect it's from the very early days of chess because it's so simple (no variations), and because of the unfashionable checking key, and because it involves only moves which have never changed in the history of chess (no queens or bishops or double-step pawn moves).