4 Tammuz 5696 ‎(24 June 1936)‎. The number 7 is a "Zayin" letter, while the number 6 is a "Vav". Both Vav and Zayin letters look very similar. I believe when Abe Sposeep commissioned the Yahrzeit plaques, somebody did a typo in the transliteration and therefore the mistake. Since the tombstone is previous to the Yahrzeit I would conclude the date of Max's death was 13 June 1937.