Missouri Revised Statutes Title XXXVIII. Crimes and Punishment; Peace Officers and Public Defenders § 572.125. Antique slot machines exempt from section 572.120, when

1. It shall be an affirmative defense to any prosecution under this chapter relating to slot machines, if the defendant shows that the slot machine is an antique slot machine and was not operated for gambling purposes while in the defendant's possession. For the purposes of this section, an antique slot machine is one which is over thirty years old.

2. Notwithstanding section 513.660,  1 whenever the defense provided by subsection 1 of this section is offered, no slot machine seized from any defendant shall be destroyed or otherwise altered until after a final court determination that such defense is not applicable. If the defense is applicable, any such slot machine shall be returned pursuant to provisions of law providing for the return of property.