The Rav noted a sefer that quoted a highly regarded Rav Landau from Nashelsk, someone the Rav was not familiar with. Not sure if this helps, but a rare sefer dated 1894 currently on auction called "et sefod" provides a eulogy for Harav Yaakov Landau, son of Harav Hagaon Avrohom Landau of Czechanow and Nasielsk.

The Rav noted a sefer that quoted a highly regarded Rav Landau from Nashelsk, someone the Rav was not familiar with. Not sure if this helps, but a rare sefer dated 1894 currently on auction called "et sefod" provides a eulogy for Harav Yaakov Landau, son of Harav Hagaon Avrohom Landau of Czechanow and Nasielsk.