For what it´s worth I consulted a French road atlas
(1:1,250,000) by L'Institut Géographique National which does show Mont Blanc
(4807m) smack on the border with Italy and Mont Blanc de Courmayeur (4748m)
just a smidgen to its south-west inside Italy, but on that scale it´s impossible
to judge the distance between them. Of more relevance to us is the
three-pointer, which appears to be Mont Dolent (an unpretentious 3823m).
Roger.