/usr/share/signify-openbsd-keys/openbsd-57-base.pub is in signify-openbsd-keys 2018.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | untrusted comment: openbsd 5.7 base public key
RWSvUZXnw9gUb70PdeSNnpSmodCyIPJEGN1wWr+6Time1eP7KiWJ5eAM
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