Open gaps of kind unmeasured: absences in the record that would change our understanding of their subject.
One open gap · one ring each, in the column of its kind · a solid ring is a gap that closedOne open gap · one ring each, in the column of its kind · a solid ring is a gap that closed
0 open · unmeasured
No gap of this kind is open. That is a fact about the record, not about the world.