If the funds or property involved are mineral proceeds, the amount for services shall not include a portion of the underlying minerals or any production payment, overriding royalty, or similar payment.
In the event that the claimant of such funds or property is deceased and did not personally agree to the fee in writing, a fee for recovery can only be collected from each identified heir, devisee or legatee that has affirmatively agreed to that fee in writing.
Okla. Stat. tit. 60, § 674.1