The Rolex perpetual watches (the movement is mechanical with automatic winding), with screw down back and screw down crown, if they have DATE, it will say Date-Just on the dial and the crystal has magnifying glass at the 3 where the aperture is located for the date, they can also come with NO DATE; they are all water resistant up to 100 meters.

Mid-Size Oyster Perpetual Plastic Crystal

It was manufactured approximately from 1960 to 1986.
The characteristics for this model are: plastic crystal ; the case measures 30 x 11.7mm.
The movement in these watches are the same as that of the ladies watches. The mid-size watches were being changed in the same way and manner as the watches for ladies.

Mid-Size Oyster Perpetual Sapphire Crystal

It was manufactured approximately from 1987 until present day.
The characteristics that are found in this model are the same as that of the Mid-Size with plastic crystal . The only difference is the sapphire crystal and the Quick Set. The bands are New Style, instead of Old Style, with Oyster, Jubilee or President band styles.

Are classified as the following categories:

1) Men's Oyster Perpetual No Date Plastic Crystal
2) Men's Oyster Perpetual Date 34mm Plastic Crystal Non Quick
3) Men's Oyster Perpetual Date 34mm Plastic Crystal Quick Set
4) Men's Oyster Perpetual Date Just 36mm Plastic Crystal Non Quick
5) Men's Oyster Perpetual Date Just 36mm Plastic Crystal Quick Set
6) Men's Oyster Perpetual Air King Sapphire Crystal
7) Men's Oyster Perpetual Date 34mm Sapphire Crystal Quick Set
8) Men's Oyster Perpetual Date Just 36mm Sapphire Crystal Quick Set

These 8 models share the following characteristics :
They are automatic , oyster perpetual for ALL categories, with screw down back and screw down crown; if with date, the crystal has magnifying glass at the aperture at 3 o'clock , and they can come with Date, Date y Date-Just depending on the model, and they are always water resistant up to 100 meters.