The Wikipedia article on abecedaria references this person and a abecedarially marked denarius he supposedly minted. The name is plausible enough for a Roman Imperial dignitary, but a cursory internet search doesn't give anything beyond this denarius tale, which makes me suspicious. Anything known about him, his dates, his cursus and possibly this denarius?
A quick search through relevant books and databases also turns up nothing. There was a monier called L. Cassius Caecianus, which might be the guy the article is referring to. However, the only denarius with his name on I can find, here, doesn't have the series of letters given on the Wikipedia page. I'm on my phone so can't pursue this further right now, but it's an interesting puzzle!