How can I get stealthVersion from bitcoin's source code?

Question

I found that a library called Bitcoinkit use stealthVersion.
Network.swift

public class Mainnet: Network {
...
    override var stealthVersion: UInt8 {
        return 0x2A
    }
...

I tried to search 0x2A,0x2a and 42(decimal from 0x2a) but find nothing in source code.

Is this calculated in bitcoin source code?

PS:
I found some Altcoin have a stealth.cpp which defined stealthversion:
(Verge)

const uint8_t stealth_version_byte = 0x28;