I was under the impression that under the old M3 system the compass was swung by the lads and signed off by their boss, who was normally the one qualified person?
Well, yes... But there is the trust that the boss was
supervising the work to his satisfaction. If the owner/pilot wishes to arrange with the signing maintainer that he does the work, and the maintainer signs for it, because it was properly
supervised, that's perfectly fine.