My wife's great-grandmother was Ida Koff Milask. The earliest record that I have found of the KOFF spelling was her death certificate. The Social Security Application for one of Ida's children gave her name as Anna Koff, and another gave it as Adele Koff. Ida/Anna/Adele had died years before her children filled out applications for Soc Sec.
Here is what I know:
Ida Koff (1870 - 30 June 1918) married Louis Milask (1866 - 2 Jan 1946). Both were born in Russia. She died in Camden, New Jersey, he in Philadelphia.
Ida's death certificate gave her parents as Simon Koff and Mollie Now(v)ak Koff.
My father-in-law (Bernard Dikter) recalls that as a young boy, his family traveling from Camden, New Jersey to the Bronx to visit his mother's (Sadie Milask Dikter) grandfather (Simon). This would have been before or around 1930. He recalls that his mother's grandfather had a long white beard. He was supposed to have been a cantor.
I have been unable to find anyone who comes close to being Simon Koff in the Ellis Island database, but it is possible that they entered the USA through Philadelphia.
Here is the ancestry:
Helene Dikter Weiner (my wife) Bernard Dikter (her father) Sadie Milask Dikter (his mother) Ida Koff Milask (her mother) Simon Koff and Mollie Now(v)ak her parents.
If any of this sounds familiar, please contact me.