The Donalds and Donald Tops
The Donalds are named after Percy Donald and his list of hills over 2000 feet in the Scottish Lowlands.
They are based on a complicated formula for determining separate hills, and originally comprised 87 hills plus a number of other named "Tops".
(Donalds appear as Class=D on this website, and Donald Tops as Class=DT).
The New Donalds
The New Donalds are an attempt to rationalize the qualifying criteria, being "hills in Central or Southern Scotland at least 2000 feet high (610m) with a drop of at least 30 metres (98 feet) all round".
All New Donalds are either a Donald or a Donald Top, but some of the Donald Tops do not qualify as New Donalds.
(New Donalds can be found by searching on Class=DN, though this does not appear in the Class column).