Thanks for the clarification, I wasn't aware of the exact time lengths that were missing, good to know.
Upon looking at the links you provided, I'm wondering if the number in the upper left (with year) are not the registration numbers. Any thoughts on that?
I also thought at first that the number in front of the year is the registration number.
But that number seems to be the running number of deaths that year. If my assumption is correct, then indeed those two could be either registered or non-registered.
I will check Danuta's Kalendarium on this. Maybe I find a further clew there.