With what I added recently you can also sort search results by year (drop-down list in top right corner of the vehicles list), that allows to see which vehicles already have a year and which ones do not.

Thanks, I didn't know that search worked like that. That will help me.

Actually you can already have those where make is know but not model name by putting "unknown" as model name on the search page (and leave make empty).
Those that do not have year but that have make and model are not in the "unknown" list.

The list of unknowns has grown to an almost unmanageable length. It will take a very long to go through it adequately. I lost interest pretty quickly. I would suggest that the unknown list be broken up into at least two parts:

One list (Unknown) would contain those cars for which we have no info at all.

The second list (additional info needed) would be where the make is known but the model, year, etc, is still needed.