Some coins are present in the catalog as "common coins", others as "Circulating commemorative coins" or "patterns" etc. Some are entered as "unknown", e.g. Saudi Arabian 1 qirsh of 1378 (this property is visible in the page "Modify or add information about this coin").
When I restrict the criteria to this particular country and year, and search for all types of coins, I see this coin in the result list. When I'm searching for all types except "common coins", this coin is not visible. When I search for "common coins" only, it is not visible again. But this is inconsistent, because it either is a common coin or not, even if we do not know what it is.
I do not know what should be modified first: the search function itself or coins that are registered as coins of unknown type.