Either last year or the year before, the then Chapter,now club, voted on a definition. As I recall, a strike must be produced under the auspices of IGT and won from their slot machines, or in the case of $200s, redeemed for strikes won from those machines. There might also be a requirement that a strike be redeemable. Maybe someone who wrote it down could post the entire definition.
Enjoy anything that meets your personal definition, because it is your collection. Even a silver toilet seat can qualify.