[Retros] 1253 last moves

[Olli Heimo]

Happy New Year. A few months ago I constructed P1356380. It shoukd be a record with 268 possible mating moves. Then I thought about maximum number of White's last moves. I have concluded to http://www.janko.at/Retros/d.php?ff=kq2Q3/NR4Q1/3Q4/B4Q2/B1Q4Q/4Q3/KQ4Q1/3R4. There I count 1253 possible White's last moves. The position is absolute. One can think that adding wN on a6 is harmless but it destroys Ka1xRa2, earlier Ra3xNa2. Black piece on b8 must be a queen. If knight or bishop, then the position is dead already before say Ka1xQa2 and a rook on b8 destroys Qc8-e8. Horizontal mirror with wK on a7 makes Kb6xPa7 imbossible. Only vertical mirror is possible. My project for 2019 is a position with maximum number of last moves without knowing who moved last. I guess that the result will be about 1500. Have those records been tried before? I can't find any attempt. Olli.