Need Help With Very Old Coin

[Acagedrebel]

I found this coin the other day in my Great Aunts attic in an old envelope nobody there knows where it came from .. I need some help trying to Identify the coin I think I can barely make out what looks like the number 20 on the back I guess is part of the date ..... Any help would be greatly appreciated....Thanks

 

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Byzantine follis justinian 40 nummi

 

[Mackaydon]

It's actually a half follis; or 20 nummi. What appears to the OP as '20' is actually part of the abbreviation 'ANNO'. The OP got the denomination right by coincidence. The reverse pic should be turned 180 degrees for proper alignment; then the "K" representing 20 nummi can be more easily seen.
Don.......

 

[Mackaydon]

Byzantine coins can be dated to within one year if the 'regnal' year of the emperor's reign and the ID of the emperor is known. The word ANNO means 'year'. The roman numeral date on the right side of the reverse is the regnal date. Simply add the regnal date to the date the emperor first became emperor and that will be the date of the coin. On the OP's coin, I can't make out the regnal date.
Don.....

 

[Acagedrebel]

Thank y’all very much y’all have been most helpful