Best Way To Get Rid Of The Green?

While not very pretty, the green color is the patina on the coins. You may just want to leave it as is.

FR has many years of experience cleaning ancient coins, knows just how far to go without hurting the coin. I also have some experience, if I were tempted to remove the green a method I use is a q-tip and some Lime Away. Diluted in water at first and depending the reaction you can increase the strength. with q-tip and solution gently rub the coin, changing the q-tip when it gets dirty. Make sure you rinse the coin afterwards.

Thanks RVFVS. That's what I was afraid of -- all green is not equal. After seeing your Gordian I had hopes of maybe finally getting this one down to where I could read enough to identify the emperor. Frustrating not to be able to read enough letters! Are they down there under the green? But don't worry -- I'm not planning on zapping this one. :-)

I'm considering x-rays.

There is more than enough "detail" visible to identify this coin.
Byzantine is not my strong suit but it looks like Justinian to me.
If you ask echizento and provide him with the specs I am sure he will grace you with a definitive ID.
This sort of glossy green is unusual on Byzantine bronzes and quite attractive.
The great "secret" to good coin conservation is working with what you got.
In this case it looks like it may well be an emerald in the rough.

Anastasius Follis AD 512-17
SB 19

One thing you will eventually learn is that certain types of coins were only produced during specific periods.
Whether we are talking about the S C reverses from Antioch or the 'good' silver antoniniani of the early 3rd century, monogram reverses of the late 4th early 5th century or in this case the larger bronzes of the early Byzantine period.
There are only so many emperors it could be based on the reverse M and the portrait with a profile.
Most Byzantine you might notice are facing portraits.
I saw the letters ST and not being particularly big on Byzantine the first thought was Justinian.
The lack of the ANNO on the left reverse and the gamma officina mark were two more clues.
Realizing that ANASTASIVS satisfied the ST clue I turned to Wildwinds and searched for a large M with gamma below and stars on either side.
It really isn't rocket science.
Just follow the clues and by process of elimination reduce the search list to a manageable size

Thanks for the lesson. I use Wildwinds a lot, but wasn't able to narrow this one down first. Learning curve will be long — but enjoyable.

What do you think about a bit of REN Wax?