I think it goes to "贤". As a native speaker I think "阮"'s possible but unlikely, since most people will write the "阝" part more straight.

I don't know Chinese but Google translate says "贤" means "virtuous", "worthy", or "able".

Is that word plausibly used to refer to devices to mean "it works" or "it passes tests"?

It's more likely to be the name of the QA person that checked it. Writing a literal "OK" is so much easier if they just wanted it mark it as good otherwise.

Ah! Thanks. I tried several different visual search methods whilst writing those post but was coming up blank.