There is a tradition of getting certification in the forms of stamps in books from master craftspersons; their experience is trusted to ascertain the stamp receiver has achieved s skill.
When we lived in small tight-knit communities, people knew whom they could turn to when they needed an expert (and whom to avoid). However, as we started moving around more and our lives and networks grew, we needed to come up with portable ways to signal our expertise to new acquaintances. Some of these original systems are still in place. For example, in Germany many carpenters still do an apprenticeship tour that lasts no less than three years and one day. They carry a small book in which they collect stamps and references from the master carpenters with whom they work along the way. The carpenter’s traditional (and now hipster) outfit, the book of stamps they carry, and — if all goes well — the certificate of acceptance into the carpenter guild are proof that here is a man or woman you can trust to build your house. (Source)
This is certification via observation, and begs some questions how this might be done digitally. The blockchain approach suggested might ascertain some authenticity of the certification, but trust requires how we value it.
(Source) MIT issues digital certificates viewable by a key or code, but the person is not identified