After the effective date of suspension of the operation of the provisions of this chapter and of the commission, as provided in Section 66662, the operations of the commission shall be wound up and any moneys remaining held by the commission, collected by assessment and not required to defray the expenses of winding up and terminating operations of the commission, shall be returned upon a pro rata basis to all handlers from whom assessments were collected in the immediately preceding current fiscal year. However, if the commission finds that the amounts so returnable are so de minimis as to make impractical the computation and remitting of such pro rata refund to such handlers, any moneys remaining after payment of all expenses of winding up and terminating operations shall be withdrawn from the approved depository and paid into the State Treasury as unclaimed trust moneys.