There is something rather unusual about the death certificate - the informant was the husband Philip Friedlander. He gave the names of Frieda's parents as unknown.
However, Philip and Frieda married in Russia, where their first 7 children were born, according to the 1910 census. Philip must have known Frieda's parents, especially since weddings were such a big deal in shtetls, and these matches between a young husband and wife were arranged by their respective families.
I suppose he might have been overwhelmed at the death of his wife, and not able to provide the information when asked about the names of Frieda's parents.
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Michele Lock
Lak/Lok/Liak/Lock and Kalon/Kolon in Zagare/Joniskis/Gruzdziai, Lithuania; Lak/Lok/Liak/Lock in Plunge/Telsiai in Lithuania
Rabinowitz in Papile, Lithuania and Riga, Latvia; Trisinsky/Trushinsky/Sturisky and Leybman in Dotnuva, Lithuania
Olitsky in Alytus, Suwalki, Poland/Lithuania; Gutman/Goodman in Czestochowa, Poland
Lavine/Lev/Lew in Trenton, New Jersey and Lida/Vilna gub., Belarus