"Today is a festival for us, the Hebrew writers dwelling in the Land of Israel. Today seventy years have been completed for one of the best among us, for Alexander Ziskind Rabinovitz." Ahad Ha'am, "A. Z. Rabinovitz (On the Completion of His Seventieth Year)," Haaretz, 24 Shevat 5684 (1924); Project Ben-Yehuda.
"Seventy years completed" on 24 Shevat 5684 = 1924 → birth on 24 Shevat 5614 = 1854. A further independent confirmation (Ahad Ha'am), alongside the autobiography and the 1875 conscription record.
Ahad Ha'am recalls that AZR was "one of the first who gathered under my banner when I founded HaShiloah (1897)," and that he enriched our literature, in recent years, "with several important volumes that he translated from German" (the translation of Baer; see "AZR the Translator").
Ahad Ha'am dwells on AZR's essay "A Blow from Our Lovers" (which he printed as "Nathan the Wise," HaShiloah vol. VII), in which AZR toppled the idol of the Haskalah, the figure of "Nathan the Wise" as the ideal of assimilation:
"Nathan the Wise is the ideal of assimilation… This idol we shall bring to the museum, to the history of our people… but in the sanctuary we shall not place him, we shall not bow down to him nor offer him sacrifices." AZR's words, quoted in Ahad Ha'am's tribute. (A national critique of the ideal of assimilation, echoing "The Land of Israel" and "For the Sake of Hebrew.")
The existence of Ahad Ha'am's reassurance letter to AZR (Igrot Ahad Ha'am II, 126) is known from a mention by Ahad Ha'am himself:
"I do not have before me now his letter to me from that time, but from my reply I see that he himself regarded his words as 'great heresy that will find no attentive ears'… and I endeavored to reassure him, that he was not already alone in this view of his (Igrot Ahad Ha'am, II, 126)." Ibid.
Thus is confirmed from a primary source the existence of Ahad Ha'am's letter → AZR from ~1901 (Igrot II, 126), concerning the essay "Nathan the Wise," beyond the verified letter of 27 Sept. 1901 (see "Ahad Ha'am's Letters").