Which preposition to use with obverse

of Occurrences 6%

The circumstance that in his case this extraordinary power was added allowed him to reveal the whole wickedness of the human will; and the sufferings of his age, as the necessary obverse of the medal, reveal the misery which is inextricably bound up with this bad will.

to Occurrences 1%

He expects no appointment or other appreciable gain through Tulpian's favour; he has no doubleness towards Felicia; there is no sneering or backbiting obverse to his ecstatic admiration.

Which preposition to use with  obverse