pgadmin3-1.20.0.dmg.sig can't be verified (while pgadmin3-1.18.1.dmg.sig can be)

Hi,

The GPG signature file "pgadmin3-1.20.0.dmg.sig" I downloaded from
http://www.postgresql.org/ftp/pgadmin3/release/v1.20.0/osx/can't be verified.  

C:\Inbox>gpg --verify pgadmin3-1.20.0.dmg.sig
gpg: WARNING: using insecure memory!
gpg: please see http://www.gnupg.org/documentation/faqs.html for more information
gpg: Signature made Fri Dec 19 19:14:58 2014 CST using RSA key ID 698F1519
gpg: Can't check signature: public key not found


However, pgadmin3-1.18.1.dmg.sig CAN be verified

C:\Inbox>gpg --verify pgadmin3-1.18.1.dmg.sig
gpg: WARNING: using insecure memory!
gpg: please see http://www.gnupg.org/documentation/faqs.html for more information
gpg: Signature made Fri Oct 11 19:25:53 2013 CST using DSA key ID 1A19643B
gpg: Good signature from "Dave Page <dpage@postgresql.org>"
gpg:                 aka "Dave Page <dpage@pgadmin.org>"
gpg:                 aka "Dave Page <dave.page@enterprisedb.com>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: 752C 3D8A 5274 C381 9231  7EAA 9602 0E04 1A19 643B


Something wrong with .sig?

Thanks