Pubkey for charlieok not on website, not signed

[matthewzipkin-bitgo]

I don't see pubkey for charlieok listed here: https://z.cash/support/pubkeys/

His signature is valid here: https://github.com/zcash/gitian.sigs/tree/master/v4.0.0_stretch/charlie

But I had to gpg --recv-keys 023B5F7BADA3AD7E0EEF46663A9B94BCF899FEB3 to find the key.

(gpg is also telling me it's expired)

$ gpg --verify zcash-4.0.0-build.assert.sig 
gpg: assuming signed data in 'zcash-4.0.0-build.assert'
gpg: Signature made Tue Sep  1 19:47:29 2020 EDT
gpg:                using RSA key 023B5F7BADA3AD7E0EEF46663A9B94BCF899FEB3
gpg:                issuer "[email protected]"
gpg: Good signature from "Charlie OKeefe (zcash gitian) <[email protected]>" [expired]
gpg: Note: This key has expired!
Primary key fingerprint: 023B 5F7B ADA3 AD7E 0EEF  4666 3A9B 94BC F899 FEB3