I would want to be able to make out the
mint mark. Maybe you can with the coin in hand, but from the photo you can tell what the first (
officina) letter is.
I am assuming it is a [ ]
SIS mark. But the first letter is not clear.
If you can't make it out you could try to clean just that portion by soaking the coin in warm water and then rubbing away at that
area with a bamboo skewer (either end - the blunt end would actually probably be better). Rub in small circular motions while it is
still wet, wipe on paper towel, repeat, and you might be able to get just a
bit more dirt off that
part.
SC