A bit of a dark aera, leech jars. Of course, if it has an inscription 'leeches' there is no mistaking them. These jars were basically counter jars in pharmacies - most of these are ceramic, some lf them were glass. They have an outward rim for tying a muslin cloth ovr them, for proper aeration. For transporting leeches there were special pewter containers. The small footless glasses with an outward rim were not leech jars but seed storage - closed with a cork fixed with a muslin cloth and kept upside down.
Leech jars are in general quite large, the beasts need their exercise. Not quite sure what the smallest properly identified leech jar is. Other counter jars may have similar shapes, so confusion lurks.