BoseX, the placard against spins for your 172... is it original from Cessna? Or perhaps associated with an STC'd mod (engine change or STOL kit)?
Yep its a Cessna original limitation. Its a 210HP Hawk XP, 6 cylinder and constant speed prop and is specifically prohibited from intentional spinning.
It would be very dangerous for us to sow the seed in peoples mind that all 172 are cleared for intentional spinning.