This would be considered a "blackjack" under Colorado law, wouldn't it?
"(a.5) “Blackjack” includes any billy, sand club, sandbag, or other hand-operated striking weapon consisting, at the striking end, of an encased piece of lead or other heavy substance and, at the handle end, a strap or springy shaft which increases the force of impact."
https://www.denver-colorado-criminal...-and-18-12-105