The clause was in the founding agreement of his company, signed in the second year of our marriage, back when the bank would not lend to him without a guarantor and I was the one still earning.
In exchange for putting my name and my credit behind the loan, the agreement gave me a thirty percent equity stake, vesting in full upon any division of marital assets. He signed it in front of a notary in a good mood, called me the smartest decision he ever made, and never read past the signature line, because reading past the signature line had always been my job.