Help With ID Of Roman Coin

It's an interesting one! The obverse isn't an emperor, but actually shows Marcus Agrippa (M AGRIPPA [F] COS[III] (meaning, Marcus Agrippa, 3 times Consul)). He was a close friend to Octavian, accomplished general and skilled architect. His wikipedia page is well worth a read. This coin was probably struck during the reign of Caligula and the obverse shows Neptune.

EDIT: here's an example in better condition:

Well done, Ben.

I doubt there could be much improvement, even by someone with a lot of experience. The only way to improve it aesthetically would be to 'smooth' it by recutting the surfaces, but this is rightfully considered sacrilegious.

In terms of care, the advice would be to keep it dry and clean. These can be handled with no concerns, especially in this condition. If you live somewhere humid or salty, it would be a good idea to wax it, but this is also frowned upon by many as it is difficult to reverse. Keep an eye out for any bright green powdery spots; this is bronze disease and would require treatment to rectify.