The model 24 is an anti-siphon vacuum breaker protected wall faucet designed for use in mild climate areas
The model 24 includes a model 34hf-ch single check anti-siphon vacuum breaker
Anti-siphon vacuum breaker - nidel model 34hf with ¾ inch male hose thread, approved under asse standard 1011, canadian standards association, listed by iapmo