"a hundred cabinet Partagas on the sideboard"
When Brideshead Revisited was written, high quality Partagás cigars were manufactured only in Cuba. They are now also made in the Dominican Republic.
A cabinet is a square Spanish-cedar (Cedrela odorata) box in which large numbers of cigars (usually 15 or more) are packed. Cigars presented in this way may be referred to as 'cabinet selection'.