The Yiddish vowel Alef would make it be pronounced Lock or Luck, not Lack. 

The record shown, has an underline which makes it Lock, however the Yiddish-English dictionary has the symbol which makes it Luck. 

The Yiddish word for curl is pronounced luck, and I do know of a Lok family who pronounces their name as Luck. 

-- 
Yitschok Margareten