Can anyone identify these bricks, which I suspect are Lego/Duplo clones. They may be more than 30 years old.
I bought them on ebay as Betta Bilda from Lego/Duplo dealer. Some BB was included, but these are unknown to me, with an extensive BB collection.
The underside of the bricks is hollow and with apparently random numbers - they aren't part numbers because they are different for the same part and sometimes the same for different parts. Window frames have no top studs.
I took a good look through many posts with similar questions, but found nothing that matched. Many Google reverse images searches kept pointing at real Lego/Duplo, before I noticed this place.
Usually I can identify unknowns like this, but these are a real challenge.