You can not add addr:housenumber if it is not signed.
You can not add addr:housenumber nor nohousenumber=yes if you are unsure if it is signed or not.

I'll go ahead and close both this and https://www.openstreetmap.org/note/3467291 . If you have time, do take a picture of these doors as they are now, so it can be verified in the future, or verify them yourself.