To bear a seal means: to have a seal imprinted, printed or otherwise put on something, like a certificate or other formal document.
It is a word used to describe what a document or media is has on it. It comes from the idea of carrying something.
Anything with a seal like that is usually an official document. Of course, official documents can be falsified. So, I can say, this certificate bears the seal of New York county and it can have been falsified, though it is not easy to falsify seals.
There are many different kinds of seals: printed (like with a rubber stamp), imprinted, engraved, carved, etc. It's an entire world of stuff.