Constant BIP16_P2SH_ACTIVATION_MAINNET 

pub const BIP16_P2SH_ACTIVATION_MAINNET: u64 = 173_805; // 173_805u64

BIP16: P2SH (Pay-to-Script-Hash) - Mainnet activation height

Starting at this block, P2SH scripts are valid. Reference: BIP16, activated April 1, 2012 at block 173,805