Extremely rare denarius, unlisted in literature, is not found in any known catalogue.
We contacted a specialist in this type of coins, Dr. Peter Ilisch and said that so far he has only seen this coin ONCE and it is an unknown variant of the coin from the Royal Mint, from the area under Cologne, around 990 AD.
Otto III (980-1002), Denarius ca. 990, Unknown mint
Obverse: O / T + T / O cross written
+ GAME + DT + REX +
Reverse: inscription S MARI А
Diameter 17 mm, weight 1.10 g