Which preposition to use with ser

of Occurrences 2%

That morning he got up and went to the temple and sent a message home to his wife that she should send him five sers of flour mixed with ghee and treacle.

por Occurrences 1%

Á no ser por ese noble distintivo, cualquiera le creería un lonjista de la calle de Culebras. ...

Which preposition to use with  ser