From GrowTomatoes.com: There are three basic sizes of fruit determined essentially by weight: beefsteak, cherry, and grape (cherry and grape are frequently considered one size type and the intermediate between beefsteak and cherry is called “cocktail”), and two shapes, oxheart and plum (Roma).
The size of a tomato fruit is determined by either its diameter or weight. The weight classes are: 2 to 5 oz, 6 to 10 oz, and greater than 10 oz. Some tomato varieties can produce fruits greater than 16 oz. Beefsteak varieties produce fruit 10 oz or greater in weight.
The diameter (millimeters, mm) fruit classifications are: extra small, 48-54 mm; small, 54-58, medium; 58-64, large, 64-73; extra large, 73-88; maximum large, >88 mm.
From Tatania's TomatoBase: 'Stupice', small, potato leaf - grower experiences (both from British Columbia) 1 lists 1-2oz; other 3-4oz.
Couldn't find a listing of diseases or any definition of size in the catalog or search box on that site. Sorry