The real thing !

I remember spending countless hours doing this with my dear grandmother . We used to travel 100 miles to visit her and I always hoped this was the first thing she would take down from a shelf on her corner cabinet !! Now , some fifty years later , it sits on my shelf and my consistency at completing it has definitely disappeared . I have completed it once , with one marble left , but not in the centre square , and I don't have my grandmother to ask if this is OK ....